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The 2023 Periodic Review of Westminster constituencies is the current cycle of the process to redraw the constituency map for the House of Commons. The process for periodic reviews of parliamentary constituencies in the United Kingdom is governed by the Parliamentary Constituencies Act 1986, as amended by the Parliamentary Voting System and Constituencies Act 2011 and subsequently by the Parliamentary Constituencies Act 2020. This review is the successor to the Sixth Periodic Review of Westminster constituencies, which was ultimately abandoned after two successive proposals by the Commissions failed to pass into law.
Under current legislation, the four Boundary Commissions of the United Kingdom are required to report on their next review of the boundaries of parliamentary constituencies before 1 July 2023. In order to meet this deadline, the Commissions began their work on 5 January 2021.
The Sixth Periodic Review of Westminster constituencies was launched by the Parliamentary Voting System and Constituencies Act 2011. The process began in 2011 and was intended to be completed by 2013, but a January 2013 vote in the House of Commons temporarily stopped the process. The process was recommenced following the 2015 general election and the four Boundary Commissions submitted their final recommendations to the Secretary of State on 5 September 2018 and made their reports public a week later. Leader of the House of Commons Andrea Leadsom told the House on 13 September 2018 that "it will be some time" before the necessary statutory instruments would be put forward for approval by both the Commons and the Lords. The proposals were never put forward for approval before the calling of the general election held on 12 December 2019, and in December 2020 the reviews were formally abandoned under the Schedule to the Parliamentary Constituencies Act 2020.
The Government's policy position regarding the process for the 2023 review was confirmed in a written statement, entitled Strengthening Democracy, by Minister of State for the Cabinet Office Chloe Smith on 24 March 2020. Smith confirmed in her written statement that primary legislation would be brought forward to remove the legal requirement to give effect to the recommendations of the Sixth Review and set the framework for future boundary reviews.
The main proposals in the statement were as follows:
Maintaining 650 seats
Under the legislation which governed the unimplemented 2018 Boundary Review recommendations, the number of constituencies was to be reduced from 650 to 600. It was proposed that this be retained at 650, on the grounds that Parliament will have a greater workload following the UK's departure from the European Union.
Electoral quota tolerance
It was proposed to maintain the current tolerance of ±5% from the average size of constituencies (the "electoral quota").
It was initially proposed that there would be no change to the four protected constituencies of Isle of Wight (divided into two seats), Na h-Eileanan an Iar (the Western Isles of Scotland) and Orkney and Shetland (the Northern Isles of Scotland), which are protected from the electoral quota due to their unique geography. However, during the passage of the legislation, an amendment was introduced to add Ynys Môn (the Isle of Anglesey in Wales), increasing the number of protected constituencies to five.
Boundary review cycle
It was proposed that reviews be carried out every eight years, rather than the current requirement of five years.
Implementation of recommendations
Currently, the final proposals of the Boundary Commissions are brought into effect through an Order in Council that must be approved by Parliament. It was proposed that the Order in Council be automatically passed in future.
|Parliamentary Constituencies Act 2020|
|Act of Parliament|
|Long title||An Act to make provision about reports of the Boundary Commissions under the Parliamentary Constituencies Act 1986; to make provision about the number of parliamentary constituencies and other rules for the distribution of seats; and for connected purposes|
|Citation||2020 c. 25|
|Introduced by||Chloe Smith, Minister of State for the Constitution and Devolution ( )|
Lord True, Minister of State for the Cabinet Office ( )
|Territorial extent||United Kingdom|
|Royal assent||14 December 2020|
|Amends||Parliamentary Constituencies Act 1986, Boundary Commissions Act 1992, Parliamentary Voting System and Constituencies Act 2011, Electoral Registration and Administration Act 2013|
Status: Current legislation
|History of passage through Parliament|
|Text of the Parliamentary Constituencies Act 2020 as in force today (including any amendments) within the United Kingdom, from legislation.gov.uk.|
A bill was introduced on 19 May 2020 to reflect the written statement and it received its Second Reading on 2 June 2020. The Parliamentary Constituencies Act 2020 received royal assent on 14 December 2020. The Act amends the regulations underpinning the upcoming boundary review process, including the Parliamentary Constituencies Act 1986, Northern Ireland Act 1998, Boundary Commissions Act 1992, and Parliamentary Voting System and Constituencies Act 2011.
A summary of the main provisions of the Act is as follows:
Each Boundary Commission must submit a report:
This gives effect to the proposal that the Orders in Council be automatically passed. The Orders must be made within four months of the reports being laid before Parliament, "unless there are exceptional circumstances".
A Boundary Commission may submit modifications to its report after it has been submitted but before an Order in Council has been drafted.
This section changes the timings of various stages in the publicity and consultation procedures.
The number of constituencies will remain at 650. Previously, the number was to be reduced to 600.
This amends the factors a Commission may take into account to include local government boundaries which are prospective on the "review date", as opposed to just being effective. Prospective local government boundaries are those which have been specified by legislation, but have not yet become effective.
This adds Ynys Môn (defined as the area of the Isle of Anglesey County Council) as a protected constituency.
For the 2023 reports, the date for determining the "electorate" to be used in the reviews is 2 March 2020 (rather than 1 December 2020). This amendment was specifically inserted partly because of the shorter time-frame for submitting the reports, but primarily because of concerns over collecting the data during the COVID-19 pandemic.
For the 2023 reports, the "review date" is specified as 1 December 2020, rather than 2 years and 10 months before the report date.
This section formally removes the duty to implement the previous reviews which were submitted in September 2018.
The four Boundary Commissions formally launched their 2023 reviews on 5 January 2021 to coincide with the release by the Office for National Statistics (ONS) of electorate data as published on 2 March 2020. The commissions jointly calculated the relevant electoral quota/range to be used for the 2023 review and the allocation of parliamentary constituencies between the four nations. The English commission further divided its allocation between the nine regions of England.
The electorate of the United Kingdom, comprising 650 constituencies, as determined by the ONS, was 47,558,398 on 2 March 2020. The electorate of the five protected constituencies – Isle of Wight (two seats), Na h-Eileanan an Iar, Orkney and Shetland, and Ynys Môn – amounted to 220,132, leaving 47,338,266 to be distributed between the remaining 645 constituencies, which gives an electoral quota of 73,393. Each non-protected constituency must have an electorate which is within 5% of this quota, which gives a permitted range of 69,724 to 77,062. In Northern Ireland the legislation allows for a wider range, in certain prescribed circumstances, from 68,313 to 77,062.
Of the 646 unprotected constituencies (Isle of Wight currently has only one seat), 236 have electorates within the permitted range, while 203 are below and 207 are above.
The regional distribution of these seats is shown in the following table.
|Region/Nation||Below range||Within range||Above range||Total seats|
|South East *||2||37||44||83|
|Yorkshire and the Humber||16||22||16||54|
The 650 constituencies were allocated between the four nations of the UK in accordance with the method of allocation specified by the legislation as shown in the table below.
|Unprotected seats||Protected seats||Total|
The Commission for England has applied the same distribution formula to the English allocation, which results in the following redistribution of constituencies among the English regions:
|South East *||83||6,522,802||89||+6||73,290|
|Yorkshire and the Humber||54||3,966,500||54||-||73,454|
|Isle of Wight||1||111,716||2||+1||55,858|
* Excluding Isle of Wight
The current constituency boundaries are largely based on the Fifth Periodic Review of Westminster Constituencies which was carried out by the Boundary Commissions between 2000 and 2007. The Scottish review was completed in time for the 2005 general election, with the other three reviews coming into effect at the 2010 general election. In England, the fifth review was based on the number of electors on the electoral register published in February 2000. The electorates were therefore already 10 years out of date by the time it came into effect, and over 20 years have now passed.
The table below shows the movements in the national/regional electorates since those used for the fifth review.
|Region/Nation||Electorate in 2000||Electorate in 2020||Absolute
|Yorkshire and the Humber||3,786,501||3,966,500||4.8%||-2.4%|
The detailed constituency and ward electorates issued by the ONS are based on the local authority boundaries which are currently effective and do not take account of prospective changes which have been enacted on 1 December 2020. There are 31 such local authorities in England, of which 16 are London Boroughs. The Commission for England subsequently worked with local authorities to produce updated data which includes these 'prospective' wards. A comprehensive list of ward electorates was published on 24 March 2021.
The initial outline timetable published by the Commission for England is as follows:
The Boundary Commission for England published their initial proposals on 8 June 2021. The proposals represent significant changes to the existing boundaries, with just 47 existing constituencies remaining unchanged (just under 10% of existing constituencies). In addition, a further 69 constituencies were unchanged except to realign boundaries with new or prospective local government ward boundaries. Due to the constraints on the size of constituency electorates, it was not always possible to allocate whole numbers of constituencies to individual counties and to avoid crossing county boundaries. Accordingly, each region was divided into sub-regions which comprised a whole number of constituencies.
The information in the table below is primarily extracted from the commission's summary sheets for each region.
|Eastern||61 (+3)||5||6||Bedfordshire and Hertfordshire (+1)
Essex and Suffolk (+1)
|East Midlands||47 (+1)||1||10||Derbyshire
Lincolnshire and Rutland (+1)
|Rutland is currently included with Leicestershire. In Northamptonshire, it has been necessary to divide three wards in order to develop a whole number of constituencies within its boundaries.|
|London||75 (+2)||2||10||North East London
Newham and Tower Hamlets (+1)
North Central and North West London
South Central and South West London (+1)
South East London
|Considerable changes required, with 31 of the proposed constituencies crossing London borough boundaries, although none cross the River Thames. It is proposed that three wards are divided across London. Among constituencies affected is that of Holborn and St Pancras – held by the Labour leader, Keir Starmer – which would be renamed Kentish Town and Bloomsbury to reflect the changes. The existing Cities of London and Westminster seat would be split between the newly named seats of City of London and Islington South, and Westminster and Chelsea East.|
|North East||27 (−2)||2||–||Newcastle upon Tyne, North Tyneside, and Northumberland
County Durham, South Tyneside, and Sunderland (−1)
Tees Valley (−1).
|As at present, no constituency crosses the River Tyne within the metropolitan county of Tyne and Wear.|
|North West||73 (−2)||10||3||Cheshire and Merseyside
Cumbria and Lancashire (−2)
|Although Merseyside and Lancashire are in separate sub-regions, a cross-county boundary constituency is proposed which combines a small part of the District of West Lancashire with the town of Southport. There are two proposed constituencies which cross the boundary between Cheshire and Merseyside, which ensures no constituencies cross the River Mersey below Warrington. It is proposed that three wards are divided – one each in Cumbria, Manchester and Wirral.
In the Wirral, the constituency of Wirral South would be broken up and divided between enlarged Birkenhead and Wirral West seats, with two wards being included in a new Ellesmere Port seat, which is mostly in Cheshire. As a consequence, the City of Chester constituency, which has been in existence since the 16th century, would be changed, with the majority of the seat forming Chester North and Neston.
|South East||91 (+7)||13||3||Berkshire, Hampshire, and Surrey (+2)
Isle of Wight (+1)
|It is proposed that three wards are divided across the region.|
|South West||58 (+3)||3||12||Avon, Somerset, and Devon (+2)
Gloucestershire and Wiltshire (+1)
|It has been possible to avoid a so-called "Devonwall" constituency, straddling Devon and Cornwall. However, considerable changes are required in Avon, Somerset and Devon. One ward has been divided in the city of Plymouth to keep changes elsewhere to a minimum.|
|West Midlands||57 (−2)||9||12||Herefordshire
Birmingham and Solihull
Staffordshire and the Black Country (−2)
|Two wards are divided in the City of Birmingham, with parts of both being included in the constituency of Birmingham Selly Oak. One ward is divided in the Black Country.|
|Yorkshire and the Humber||54 (-)||2||13||Humberside and South Yorkshire (−1)
North Yorkshire and West Yorkshire (+1)
|It has been necessary to divide a ward in each of the cities of Leeds and Sheffield and in the borough of Kirklees due to the large ward electorates in these metropolitan boroughs. The seat of Elmet and Rothwell has been split up, with Rothwell being included in a reconfigured Wakefield constituency and remaining areas comprising parts of two proposed constituencies which span the county boundary between North Yorkshire and West Yorkshire. Don Valley would be replaced by Doncaster East and Axholme, which spans the boroughs of Doncaster and North Lincolnshire.|
Initial proposals were published on 20 October 2021. As the number of constituencies in Northern Ireland remains the same, changes were only necessary to bring some of the electorates within the permitted range and align boundaries with those of revised local government wards. Major proposed changes are enlarging Strangford to include Lecale and renaming it 'Strangford and Quoile'. Belfast South would be enlarged into the countryside and renamed 'Belfast South and Mid Down'. East Antrim would be extended further west, while Fermanagh-South Tyrone would be extended further east into County Armagh.
The Boundary Commission for Scotland released its initial proposals on 14 October 2021.
The following table details the proposed changes, based on the commission's press release.
|Region||Number of constituencies||Number unchanged||Comments|
|Aberdeen City, Aberdeenshire, Argyll and Bute, Highland, and Moray||9 (-1)||1||The two Aberdeen City constituencies were realigned to ward boundaries, except near Rosemount. Argyll and Bute was renamed Argyll and expanded northward. Gordon was expanded westward and renamed Gordon and Moray South. Highland is divided into three constituencies, with part of Moray centred on Elgin included in a Highland constituency.|
|Angus, Clackmannanshire, Dundee City, Falkirk, Fife, Perth and Kinross, Stirling, and West Lothian||13 (-)||1||Dundee's east–west split was maintained and largely aligned with ward boundaries. Parts of Angus were added to Dundee East (renamed Dundee East and Arbroath). In Falkirk, Bo'ness was added to Linlithgow and East Falkirk, while Whitburn was added to Livingston in West Lothian. Stenhousemuir and its vicinity were added to Clackmannanshire council area in a proposed Mid Forth Valley constituency. Angus was renamed Angus and Strathmore and added Blairgowrie in Perth and Kinross.|
|Dumfries and Galloway, East Dunbartonshire, North Lanarkshire, Scottish Borders, South Lanarkshire, and West Dunbartonshire||12 (-)||0||The boundaries in Dumfries and Galloway and Scottish Borders remained largely unchanged. East Dunbartonshire and part of North Lanarkshire were split between two constituencies. The remainder of North Lanarkshire was added to South Lanarkshire constituencies. The West Dunbartonshire council area received its own constituency, along with part of Yoker (in Glasgow).|
|City of Edinburgh, East Lothian, and Midlothian||7 (-)||2||The majority of the boundary changes occurred with the City of Edinburgh, but all constituency names remained the same. In East Lothian, part of Musselburgh was added to the Edinburgh East constituency. The present constituency of East Lothian is renamed East Lothian Coast and contains the remainder of the council area.|
|East Ayrshire, North Ayrshire, and South Ayrshire||4 (-)||4||The four constituencies within this region remain unchanged.|
|East Renfrewshire||1 (-)||1||The council area will continue to have its own constituency.|
|Glasgow City, Inverclyde, and Renfrewshire||9 (-1)||1||The constituencies in this area were nearly completely reorganized. Six constituencies exist wholly within Glasgow. Glasgow North West saw the least change but was renamed Glasgow West. Yoker in Glasgow was added to West Dunbartonshire. The Inverclyde constituency was expanded to include Bridge of Weir and Houston in Renfrewshire, while Cardonald in Glasgow was added to Renfrew North (renamed from Paisley and Renfrewshire North). Paisley and Renfrewshire South was renamed Renfrew South.|
|Na h-Eileanan an Iar and Orkney and Shetland||2||2||These constituencies remain protected by UK law.|
Initial proposals for constituencies in Wales were published on 8 September 2021, reducing Wales' constituencies by 8, from 40 to 32.
Apart from the protected constituency of Ynys Môn, no constituencies are unchanged. The table below summarises the relationship between the remaining current constituencies and the initial proposals.
|Current constituency||Proposed constituency|
|Expanded constituencies - containing an entire current constituency and parts of adjoining constituencies|
|Alyn and Deeside||Alyn and Deeside|
|Blaenau Gwent||Blaenau Gwent and Rhymney|
|Brecon and Radnorshire||Brecon and Radnor|
|Cardiff Central||Cardiff Central|
|Cardiff North||Cardiff North|
|Cardiff West||Cardiff West|
|Dwyfor Meirionnydd||Dwyfor Meirionnydd|
|Montgomeryshire||Montgomeryshire and Glyndwr|
|Redefined constituencies - containing a majority of at least one constituency and parts of adjoining constituencies|
|Caerphilly||Newport West and Caerphilly|
|Cardiff South and Penarth||Cardiff South and Penarth|
|Carmarthen East and Dinefwr||Caerfyrddin|
|Gower||Swansea West and Gower|
|Merthyr Tydfil and Rhymney||Merthyr Tydfil and Aberdare|
|Neath||Swansea East and Neath|
|Newport East||Newport East|
|Preseli Pembrokeshire||Mid and South Pembrokeshire|
|Swansea East||Swansea Central and North|
|Vale of Glamorgan||Vale of Glamorgan2|
|Abolished constituencies - split between two or more proposed constituencies|
|Carmarthen West and South Pembrokeshire|
|Vale of Clwyd|
1 The proposed constituency of Bridgend contains the majority of the current constituency of Ogmore and a minority of the current constituency of Bridgend (including the town of Bridgend). The current constituency is effectively abolished, with the majority being included in the proposed constituency of Aberafon Porthcawl.
2 The proposed constituency of Vale of Glamorgan contains the majority of the existing constituency, but no part of any other constituency.
According to analysis carried out in October 2021 by electoral modelling consultancy Electoral Calculus, a total of 28 constituencies would disappear (i.e. be broken up and not form the larger part of any proposed seats), offset by 28 wholly new constituencies (proposed seats which don't contain the larger part of any pre-existing seat). If the 2019 general election was re-run under the boundaries in the initial proposals, it is estimated that a further 23 seats would change hands. The overall effect would be a net gain of 13 seats for the Conservatives, a net loss of 8 for Labour, a loss of 3 for the Liberal Democrats and 2 for Plaid Cymru. This is further analysed as follows:
|Seats changing hands||Total|
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