|United Kingdom Parliamentary Constituencies|
|Number||650 (as of 2021)|
|Populations||20,887 (Na h-Eileanan an Iar) - 113,021 (Isle of Wight)|
The Parliament of the United Kingdom currently has 650 parliamentary constituencies across the constituent countries (England, Scotland, Wales and Northern Ireland), each electing a single member of parliament (MP) to the House of Commons by the plurality (first past the post) voting system, ordinarily every five years. Voting last took place in all 650 of those constituencies at the United Kingdom general election on 12 December 2019.
The number of seats rose from 646 to 650 at the 2010 general election after proposals made by the boundary commissions for England, Wales and Northern Ireland (the Fifth Periodic Review of Westminster constituencies) were adopted through statutory instruments. Constituencies in Scotland remained unchanged, as the Boundary Commission for Scotland had completed a review just before the 2005 general election, which had resulted in a reduction of 13 seats.
Primary legislation provides for the independence of the boundary commissions for each of the four parts of the UK; the number of seats for each of the countries; permissible factors to use in departing from any old boundaries; and a strong duty to consult. The Fifth Review was governed by the Parliamentary Constituencies Act 1986. Under the Parliamentary Voting System and Constituencies Act 2011, as amended by the Parliamentary Constituencies Act 2020, the number of MPs is now fixed at 650. The Sainte-Laguë formula method is used to form groups of seats split between the four parts of the United Kingdom and the English regions (as defined by the NUTS 1 statistical regions of England).
The table below gives the number of eligible voters broken down by constituent country, including the average constituency size in each country.
|Total electorate for each constituent country|
|Average electorate per constituency for each constituent country|
|Overall UK average||68,184||—||70,547||—||71,314||—||70,997||—||73,181||—|
Geographical size of constituencies
The constituencies vary considerably in size. The one with the greatest geographical area is Ross, Skye and Lochaber, at about 12,000 square kilometres (4,600 sq mi). The largest in Wales is Brecon and Radnorshire. The smallest constituency by area is Islington North at 7.35 square kilometres (2.84 sq mi).
Parliamentary constituencies in the United Kingdom
The "Region" of the table refers to the NUTS 1 statistical region of England, which coincides with the former European Parliament constituency that the constituency was situated in until 31 January 2020.
As of the 2019 election there are 533 constituencies in England, 40 in Wales, 59 in Scotland and 18 in Northern Ireland.
Summary of main boundary changes for the 2010 general election
- Scotland – No changes from 2005 election.
- Wales – Number of seats unchanged: three seats were abolished and three were created: Aberconwy, Arfon, and Dwyfor Meirionnydd.
- Northern Ireland – No extra or fewer seats allocated.
- The non-metropolitan counties of Cornwall, Derbyshire, Devon, Essex, Hampshire, Lancashire, Norfolk, Northamptonshire, Warwickshire and Wiltshire each gained one seat.
- Following the abolition of the county of Avon, each of the four successor authorities (Bristol, South Gloucestershire, Bath and North East Somerset, and North Somerset) were considered separately, resulting in significant changes, gaining one seat overall.
- The metropolitan counties of Greater Manchester, Merseyside, Tyne and Wear, South Yorkshire, West Midlands and West Yorkshire each lost a seat.
- Inner London gained one seat while northern and eastern parts of Outer London each lost one.
- The City of York was reviewed separately and was divided into two seats, neither overlapping part of North Yorkshire.
- Herefordshire and Worcestershire, to reflect their full reinstatement as separate counties, were considered in separate reviews, leading to Herefordshire being split into two constituencies, each entirely within the county.
- Isle of Wight maintained its status as one constituency, the largest by electorate.
Current boundary reviews
The Boundary Commissions submitted their final proposals in respect of the Sixth Periodic Review of Westminster Constituencies (the 2018 review) in September 2018. Although the proposals, which would have reduced the number of seats to 600, were immediately laid before Parliament they were not brought forward by the Government for approval. Accordingly, they did not come into effect for the 2019 election which took place on 12 December 2019, which was contested using the constituency boundaries in place since 2010.
Under the terms of the Parliamentary Constituencies Act 2020, the Sixth Review was formally abandoned and the specified number of constituencies reverted to the current level of 650. The strict electoral parity requirement was retained, providing that the electorate of all constituencies should be within a range of 5% either side of the electoral quota.
- List of former United Kingdom Parliament constituencies
- Member of Parliament
- Lists of electoral districts by nation
- United Kingdom general elections overview
- "The Parliamentary Constituencies and Assembly Electoral Regions (Wales) Order 2006". www.legislation.gov.uk.
- "The Parliamentary Constituencies (England) Order 2007". www.legislation.gov.uk.
- "The Parliamentary Constituencies (England) (Amendment) Order 2009". www.legislation.gov.uk.
- "The Parliamentary Constituencies (Northern Ireland) Order 2008". www.legislation.gov.uk.
- "A Guide to the 2013 Review" The Boundary Commission for England — retrieved 2012-12-19.
- "Electoral statistics, UK: 2017". ONS. Retrieved 7 August 2018.
- Baker, Carl; Uberoi, Elise; Cracknell, Richard (28 January 2020). "General Election 2019: full results and analysis". Cite journal requires
- "Parliamentary constituencies". www.parliament.uk. Retrieved 13 July 2019.
- "Hansard: 2 Jul 2001 : Column 82". www.parliament.uk. Hansard. Retrieved 13 July 2019.
- "2023 Review | Boundary Commission for England". Retrieved 1 April 2021.
- Boundary Commission for N.I. Fifth Periodical Report (HM Command Paper 73) – Parliamentary Constituencies of Northern Ireland. Retrieved 2013-07-19.