2023 Periodic Review of Westminster Constituencies
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2023 Periodic Review of Westminster Constituencies

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.[1] 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.[1] In order to meet this deadline, the Commissions began their work on 5 January 2021.

Previous review

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[2][3] and made their reports public a week later.[4][5][6][2] 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.[7] 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.[1]

Proposed changes

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.[8] 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.[9]

Electoral quota tolerance

It was proposed to maintain the current tolerance of ±5% from the average size of constituencies (the "electoral quota").

Protected constituencies

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.[8] 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.[10]

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.


A Bill of Parliament was introduced on 19 May 2020[11] to reflect the written statement and it received its Second Reading on 2 June 2020.[12] The Parliamentary Constituencies Act 2020 received royal assent on 14 December 2020.[13] 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 are as follows:

Clause 1 - Reports of the Boundary Commissions

Each Boundary Commission must submit a report:

(a) before 1 July 2023,

(b) before 1 October 2031, and

(c) before 1 October of every eighth year after that.

Clause 2 - Orders in Council giving effect to reports

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".

Clause 3 - Modifications of recommendations in reports

A Boundary Commission may submit modifications to its report after it has been submitted but before an Order in Council has been drafted.

Clause 4 - Publicity and consultation

This clause changes the timings in respect of various stages in the publicity and consultation procedures.

Clause 5 - Number of parliamentary constituencies

The number of constituencies will remain at 650.

Clause 6 - Taking account of local government boundaries

This amends the rules regarding 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.

Clause 7 - Protected constituencies

This adds Ynys Môn (defined as the area of the Isle of Anglesey County Council) as a protected constituency.

Clause 8 - Registers used to determine the "electorate" in relation to the 2023 reports

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.[12]

Clause 9 - Alteration of the "review date" in relation to the 2023 reports

For the 2023 reports, the "review date" is specified as 1 December 2020, rather than 2 years and 10 months before the report date.

Clause 10 - Removal of duty to implement etc. in relation to current reports

This clause formally removes the duty to implement the previous reviews which were submitted in September 2018.

The reviews

The four Boundary commissions formally launched their 2023 reviews on 5 January 2021[14][15][16][17] to coincide with the release by the Office for National Statistics (ONS) of electorate data as published on 2 March 2020.[18] 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.

Size of 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 electoral range of 69,724 to 77,062.[14] In Northern Ireland the legislation allows for a wider range, in certain prescribed circumstances, from 68,313 to 77,062.[17]

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
Eastern 7 25 26 58
East Midlands 7 17 22 46
London 20 20 33 73
North East 21 6 2 29
North West 28 33 14 75
South East * 2 37 44 83
South West 7 23 25 55
West Midlands 25 26 8 59
Yorkshire and the Humber 16 22 16 54
England 133 209 190 532
Northern Ireland 6 8 4 18
Scotland 27 18 12 57
Wales 37 1 1 39
Total 203 236 207 646

Distribution of seats

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

United Kingdom

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.[19]

Nation Current seats


Unprotected seats Protected seats Total
Electorate Allocation Average size Electorate Allocation Electorate Allocation Change
England 533 39,748,705 541 73,473 111,716 2 39,860,421 543 +10
Northern Ireland 18 1,295,688 18 71,983 - - 1,295,688 18 -
Scotland 59 4,023,611 55 73,320 56,001 2 4,079,612 57 -2
Wales 40 2,270,262 31 73,234 52,415 1 2,322,677 32 -8
Total 650 47,338,266 645 73,393 220,132 5 47,558,398 650 -

Regions of England

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:[19]

Region Current seats


Electorate Allocation Change Average size
Eastern 58 4,482,127 61 +3 73,477
East Midlands 46 3,481,126 47 +1 74,067
London 73 5,550,454 75 +2 74,006
North East 29 1,952,999 27 -2 72,333
North West 75 5,381,549 73 -2 73,720
South East * 83 6,522,802 89 +6 73,290
South West 55 4,242,136 58 +3 73,140
West Midlands 59 4,169,012 57 -2 73,141
Yorkshire and the Humber 54 3,966,500 54 - 73,454
Unprotected seats 532 39,748,705 541 +9 73,428
Isle of Wight 1 111,716 2 +1 55,858
Total 533 39,860,421 543 +10 73,408

* Excluding Isle of Wight

Prospective wards

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,[20] of which 16 are London Boroughs.[21] 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.[20]


The initial outline timetable published by the Commission for England is 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.
  • June 2023: Submit and publish final report and recommendations.[22]

Comparison with the Fifth Review

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 3 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.[23] 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[18] Absolute

% increase


% increase

Eastern 4,063,594 4,482,127 10.3% 2.8%
East Midlands 3,198,214 3,481,126 8.8% 1.4%
London 4,974,025 5,550,454 11.6% 4.0%
North East 1,955,336 1,952,999 -0.1% -6.9%
North West 5,193,017 5,381,549 3.6% -3.4%
South East 6,021,130 6,634,518 10.2% 2.7%
South West 3,779,970 4,242,136 12.2% 4.6%
West Midlands 4,023,708 4,169,012 3.6% -3.5%
Yorkshire and the Humber 3,786,501 3,966,500 4.8% -2.4%
England 36,995,495[23] 39,860,421 7.7% 0.4%
Northern Ireland 1,097,450[24] 1,295,688 18.1% 10.0%
Scotland 3,995,489[25] 4,079,612 2.1% -4.9%
Wales 2,225,599[26] 2,322,677 4.4% -2.8%
Total 44,314,033 47,558,398 7.3% 0.0%


  1. ^ a b c "Parliamentary Constituencies Act 2020".
  2. ^ a b "2018 Review". Boundary Commission for Northern Ireland. 16 February 2016. Retrieved 2018.
  3. ^ "Towards final recommendations (and beyond)". Boundary Commission for England. Retrieved 2018.
  4. ^ "2018 Review". Boundary Commission for England. Boundary Commission for England. Retrieved 2018.
  5. ^ "2018 Review of Westminster Constituencies". Boundary Commission for Scotland. Retrieved 2018.
  6. ^ "2018 Review of Parliamentary constituencies". Boundary Commission for Wales. Archived from the original on 18 October 2016. Retrieved 2018.
  7. ^ Business of the House - Hansard hansard.parliament.uk
  8. ^ a b Smith, Chloe (20 March 2020). "Update: Strengthening Democracy:Written statement - HCWS183". Parliament.uk. Parliament of the United Kingdom. Retrieved 2020.
  9. ^ Proctor, Kate (26 March 2020). "MPs no longer to get automatic vote on constituency boundary plans". The Guardian.
  10. ^ Wells, Ione (30 June 2020). "Ynys Môn constituency 'protected' from cut in number of MPs". BBC News. Retrieved 2020.
  11. ^ "Parliamentary Constituencies Bill". parliament.uk. Retrieved 2020.
  12. ^ a b "Parliamentary Constituencies Bill - Tuesday 2 June 2020 - Hansard - UK Parliament". hansard.parliament.uk. Retrieved 2021.
  13. ^ "Parliamentary Constituencies Act 2020". legislation.gov.uk. Retrieved 2020.
  14. ^ a b "2023 Review launched". Boundary Commission for England. Retrieved 2021.
  15. ^ "2023 Review of UK Parliament Constituencies". Boundary Commission for Scotland. Retrieved 2021.
  16. ^ "2023 Review". Boundary Commisison for Wales. Retrieved 2021.
  17. ^ a b "2023 Review: Electoral Quota and Allocation of Constituencies Announced". Boundary Commission for Northern Ireland. 5 January 2021. Retrieved 2021.
  18. ^ a b "Electoral statistics, UK". Office for National Statistics. Retrieved 2021.
  19. ^ a b "2023 Review". Boundary Commission for England. Retrieved 2021.
  20. ^ a b "Data and resources". Boundary Commission for England. Retrieved 2021.
  21. ^ "Electoral Changes Orders 2020".
  22. ^ "2023 Review". Boundary Commission for England. Retrieved 2021.
  23. ^ a b Boundary Commission for England. "Fifth Periodic Review" (PDF).
  24. ^ Boundary Commission for Northern Ireland. "Fifth Periodic Review".
  25. ^ Boundary Commission for Scotland. "Fifth Periodic Review".
  26. ^ Boundary Commission for Wales. "Fifth Periodic Review".

External links

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