Boundary commissions (United Kingdom)

[2] The boundary commissions, which are required to report every eight years, must apply a set series of rules when devising constituencies.

Firstly, each proposed constituency has to comply with two numerical limits: There are a small number of exceptions to the numerical limit on electorate which are specified in the legislation: Having satisfied the electorate and area requirements, each commission can also take into account a number of other factors: As these factors can to an extent be mutually conflicting, each commission has discretion on how it applies them.

The new procedures further strengthen the separation of the creation of constituency boundaries from those elected for the resulting electoral areas, with the aim of eliminating any scope for gerrymandering.

Customarily, each commission conducted a complete review of all constituencies in its part of the United Kingdom every eight to twelve years.

In January 2013, parliamentary opposition to proposed legislative amendments because of a lack of consensus in the coalition resulted in the review being suspended.

Following the Conservative victory at the 2015 general election, the review was recommenced in 2016 and final recommendations were submitted by the four commissions in September 2018 and laid before Parliament.

However the revised proposals were never brought forward by the Government for approval and, further to the passing of the Parliamentary Constituencies Act 2020, the Sixth Review was formally abandoned.

[17] The final consultation for England began on 8 November 2022 with the publication of the Revised Proposals and lasted for four weeks, ending on 5 December.

[23] The scope of the boundary commissions' work is limited to areas for election to the UK House of Commons.

The Act also specifies that the constituencies are grouped into eight regions to allow the return of list members elected by proportional representation to the parliament.

The Act required the Boundary Commission for Wales to group the constituencies into electoral regions, to allow the return of list members elected by proportional representation to the Assembly.

The Boundary Commission for Wales's Fifth General Review resulted in revised Assembly constituencies and electoral regions.

The Parliamentary Voting System and Constituencies Act 2011 removed the link with Westminster constituencies, and the Senedd Cymru (Members and Elections) Act 2024 made the Democracy and Boundary Commission Cymru the statutory review body for Senedd boundaries.