2023 Periodic Review of Westminster constituencies

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.[15] In Northern Ireland the legislation allows for a wider range, in certain prescribed circumstances, from 68,313 to 77,062.[18]

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.

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.[20]

Map showing the impact by nation and region of the UK.

  region gaining 5 or more seats

  region gaining 2-4 seats

  region gaining 1 seat

  region keeps the same number of seats

  region loses 2-4 seats

  region loses 5 or more seats

  protected Island constituencies that are unaffected by the changes

The Commission for England applied the same distribution formula to the English allocation, which results in the following redistribution of constituencies among the English regions:[20]

* Excluding Isle of Wight

The current constituency boundaries were 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of electors on the electoral register published in February 2000.[21] The electorates were therefore already 10 years out of date by the time it came into effect, and over 20 years had passed.

The table below shows the movements in the national/regional electorates since those used for the fifth review.

The detailed constituency and ward electorates issued by the ONS were based on the local authority boundaries which are currently effective and do not take account of prospective changes which were enacted on 1 December 2020. There are 31 such local authorities in England,[25] of which 16 are London boroughs.[26] 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.[25]

The initial outline timetable published by the Commission for England was as follows:

• January 2021: Begin development of initial proposals.
• 10 May 2021: Publish Guide to the 2023 Review.
• 8 June 2021: Publish initial proposals and conduct eight-week written consultation.
• Early 2022: Publish responses to initial proposals and conduct six-week 'secondary consultation', including between two and five public hearings in each region.
• Late 2022: Publish revised proposals and conduct four-week written consultation.
• 27 June 2023: Submit and publish final report and recommendations.[27]

The Boundary Commission for England published their initial proposals on 8 June 2021.[28] The proposals represent significant changes to the existing boundaries, with just 47 existing constituencies remaining unchanged (just under 10% of existing constituencies[29]). 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.[29] Accordingly, each region was divided into sub-regions which comprised a whole number of constituencies.

The information in the table below was primarily extracted from the commission's summary sheets for each region.

Initial proposals were published on 20 October 2021.[42] 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. 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.[43]

The Boundary Commission for Scotland released its initial proposals on 14 October 2021.[44][45]

The following table details the proposed changes, based on the commission's press release.[44]

Initial proposals for constituencies in Wales were published on 8 September 2021, reducing Wales' constituencies by 8, from 40 to 32.[46][47]

Apart from the protected constituency of Ynys Môn, no constituencies were unchanged. The table below summarises the relationship between the remaining current constituencies and the initial proposals.

Notes:

¹ The proposed constituency of Bridgend contained 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 was effectively abolished, with the majority being included in the proposed constituency of Aberafon Porthcawl.

² The proposed constituency of Vale of Glamorgan contained 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 do not 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 was 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.[48] This was further analysed as follows:

The Commission for England published revised proposals on 8 November 2022, followed by a third and final, four-week, consultation period ending on 5 December. After receiving over 45,000 comments over the previous two consultation periods, the Commission revised nearly half the proposed constituencies put forward in its initial review (including name changes).[55][56] Of the 225 constituencies whose boundaries were revised, 90 have revised names. A further 34 constituencies changed names only. 55 of the 124 name changes reverted to the current constituency names, either because the revised constituency boundaries were more closely aligned with the current boundaries, or because local residents objected to the new names put forward by the Commission. More extensive use of divided wards was included in the revised proposals, totalling 47, compared to 19 in the initial proposals. This enabled more communities to be kept together in one constituency and also meant that constituencies in some areas could more closely follow the existing configurations, resulting in fewer voters moving between seats.

The information in the table below was primarily extracted from the commission's summary sheets for each region.

The Commission for Northern Ireland published revised proposals for consultation on 14 November 2022.[66]

Minor amendments were made to eight of the 18 constituencies, making more use of divided wards to minimise the changes necessary to the current configuration of constituencies. As a result of the revisions, the proposed name of the Strangford and Quoile constituency reverted back to its current name of Strangford.

The Commission for Scotland also published revised proposals for consultation from 8 November to 5 December 2022.[67]

Of the 55 mainland constituencies, 20 were unchanged from the initial proposals, including three with changed names only. Of the 35 revised constituencies, 20 also have revised names. There were no changes to the proposed groupings of council areas, but only the Ayrshire and East Renfrewshire groupings were completely unaffected.

The final proposals were announced in June 2023.[68]

The Commission for Wales published revised proposals on 19 October 2022, with comments due no later than 15 November.[69]

The Commission revised its initial proposals in terms of their geographical make-up in 22 of the 32 allocated constituencies, and 9 of the proposed constituency names were amended.[70] Most of the adjustments resulted from moving electoral wards between neighbouring constituencies. The most significant change was combining western parts of Newport with the majority of the existing constituency of Islwyn, rather than parts of Caerphilly, on the basis of better local ties, to form Newport West and Islwyn. The existing constituency of Caerphilly is retained with relatively minor changes composed wholly of wards of Caerphilly County Borough Council.[71] There were also some boundary realignments in North Wales.

According to Electoral Calculus, the revised proposals result in four fewer new and abolished seats (24 v 28) and seven fewer seats changing hands (16 v 23). Overall, compared to the initial proposals, this would result in three fewer seats won by the Conservative party at the 2019 general election and three fewer lost by the Labour party, resulting in a net gain of ten for the Conservatives and a net loss of five for Labour. In November 2022, professors Colin Rallings and Michael Thrasher estimated the Conservatives would have won five additional seats in 2019, with Labour unchanged.[56]

In England, after receiving a further 18,890 representations,[76] 41 constituencies were revised, eight of which also involved a change of name. Most of these were relatively minor boundary changes between two neighbouring seats. In a further 45 constituencies, only the name was changed.[2] This left 457 seats unaltered from the revised proposals published in November 2022. The final recommendations for England result in only 55 of the existing 533 constituencies remaining completely unchanged.[77]

In Wales, 21 of the 32 seats were unaltered from the revised proposals; 10 had revised boundaries (of which five were renamed); and one had a name change only.[75] In Scotland boundary changes affected 18 seats, of which 12 were renamed. Only name changes affected a further six, leaving 33 unaltered. In Northern Ireland, minor boundary changes affected five seats, with no changes to the proposed names.

The final recommendations on the new constituencies in Wales were published on 28 June 2023 by the Boundary Commission for Wales.[78][79] This followed years of proposals and consultations since 2021, with initial proposals published in 2021[80] and revised in 2022.[81]

Legend – New constituency; expanded constituency; redefined constituency; revived constituency

Following the publication of the final recommendations, these are the new or re-established names of constituencies which will be fought at the next general election:

The following constituency names will no longer exist at the next general election:

Most of the new seats listed above are the result of name changes to existing constituencies following boundary changes of varying degrees, including five where the boundaries are unchanged. An existing seat where no part forms the largest part of any new seat is considered to be "disappearing". Conversely, any new seat which doesn't contain the largest part of any existing seat is considered to be genuinely "newly created".

The table below lists the disappearing and newly created constituencies.[82]

An existing seat can be regarded as being linked to a newly named seat where part of the existing seat contributes the largest part of the newly named seat. There are a total of 187 linked constituencies, many of which involve significant changes resulting from the knock-on impact of new or abolished seats within review areas. However, some arise from the consultation process and involve only minor changes. The table below lists those constituencies with name changes, indicating the extent of the changes by reference to the proportion of the old constituency included in the new constituency, or the proportion of the new in the old, which ever is the lesser:

• None - name change only
• Minor - greater than 90%
• Moderate - between 75% and 90%
• Major - between 50% and 75%
• Wholesale - less than 50%

Sources:

• Electoral Calculus - New Constituency Boundaries for 2023[83]
• House of Commons Library - Boundary review 2023: Which seats will change in the UK?[84]