The United Kingdom is currently divided into 650 parliamentary constituencies. One Member of Parliament in the House of Commons represents a single constituency.
Parliamentary constituency boundaries are reviewed periodically. The 2024 general election in the UK was contested on a new set of boundaries, resulting from the 2023 Periodic Review of Westminster constituencies. The total number of seats, and so the total number of MPs, was not changed from the number set by the Fifth Periodic Review of Westminster constituencies. The allocation of seats between each of the nations of the UK is based on the proportion of the UK registered electorate. For the 2024 general election the allocation for Northern Ireland was unchanged, England increased by 10 and Scotland decreased by two. The number of seats in Wales was reduced from 40 to 32, ending the over-representation of Wales 25 years after devolution.
Section 3 of the Parliamentary Constituencies Act 1986, as amended, determines the frequency of current reviews. Currently, reviews should occur every eight years. For more information on boundary reviews, see the Commons Library research briefing, Constituency boundary reviews and the number of MPs.
The Acts of Union 1800 merged the separate British and Irish Parliaments into a single Parliament of the United Kingdom, with effect from 1 January 1801. The first House of Commons of the United Kingdom was composed of all 558 Members of the former Parliament of Great Britain and 100 of the Members of the House of Commons of Ireland. In the 19th century, changes were linked to the disenfranchisement for corruption of constituencies and to the re-allocation of seats. Following the Redistribution of Seats Act 1885, most constituencies by law returned a single MP to Parliament, although 23 constituencies, including the City of London and Bath, returned two Members until 1910.
The redistribution of seats that occurred in 1917-18 was based on population and led to a growth in the number of seats in the House of Commons to 707. The creation of the Irish Free State in 1922 caused the reduction in House of Commons seats from 707 to 615. There was a steady increase in the number of Parliamentary constituencies from 625 in 1950, to 659 from 1997. It remained at 659 until 2005. In 2005 the number dropped to 646. This followed the re-establishment of the Scottish Parliament and the associated reduction in the number of Scottish seats in Westminster. In 2010 the number of seats increased to 650, the current number.
The downloadable Excel file includes two tables. Table 1 lists the number of seats contested in general elections to the House of Commons from 1801 to today. Table 2 provides details of legislation amending the number of seats. Source details are available in the Excel file.
Parliament: facts and figures
The Parliament: facts and figures series covers topics including elections, government, legislation, Members and parliamentary business.
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