Proposed Constituency Boundaries 2018

This page first posted 30 May 2016, last updated 27 April 2020

New Boundaries 2018 Introduction

Following the passage of the Parliamentary Voting System and Constituencies Act, the four national Boundary Commissions were asked to undertake the "2018 Review" of contituency boundaries to equalise the size of seat both within and between the four nations of the UK. The Boundary Commissions are independent bodies who put considerable effort into drawing up boundaries in a generally fair way, reflecting local geography and affiliations. There are two consultation periods where comments and objections to the proposals can be brought forward for consideration.

The Boundary Commission of England published its initial set of proposals on 13 September 2016, with final proposals being ready by September 2018. The Welsh Boundary Commission also published their initial proposals on the same day. The Boundary Commission for Northern Ireland published its initial proposals on 6 September 2016. The Scottish Boundary Commission is published its initial proposals on 20 October 2016.

Revised proposals were published by the English, Scottish and Welsh Boundary Commissions on 17 October 2017. Revised proposals were published by the Northern Ireland Boundary Commission in January 2018.

Final proposals were published by all four Boundary Commissions on 10 September 2018. The analysis below is based on these final proposals.

Next review in 2023

Nonetheless, the government did not push forward with acceptance of the new 2018 boundaries, and the 2019 General Election was run using the existing boundaries, which have been in use since 2010.

In March 2020, the government announced (full text) that it is going to restart the stalled programme of new boundaries for Westminster constituencies. This new review, which is yet to be legislated for, will keep the number of seats at 650 and not reduce them to 600 as had been planned by David Cameron's coalition government. The strict 5pc tolerance on seat electorates will be retained, but future reviews will take place every eight years, rather than every five years.

The next Boundary Review is expected to start in early 2021 and to report by October 2023. See our full analysis of 2023 review.

Seat Totals by Nation

The total number of seats per consituent part of the country is already known:

This page contains full details of these reviews as they are published.

Executive Summary

The Boundary Commissions have now all published their initial proposals. This allows us to get a good overall view of the likely outcome. In terms of the headline impact on seats nationally the implied result of the 2019 general election, as if it had been run under the new boundaries, is:

The Conservatives would change from having a majority of 80 seats out of 650 to having a majority of 104 seats out of 600. That would be more like a landslide result, where the Conservatives would win more than twice the number of seats of Labour.

The analysis below shows which seats "disappear" under the boundary changes, which seats switch party allegiance, and which fresh seats are newly created.

Area by area

Area by area, the net change in seats is shown in this table:

There are full regional pages of explanation and seat breakdowns available. Just click on the region's name in the left-hand column of the table.

Generally, the regions of northern England and London lose the most seats, while southern England loses fewer seats. Since the former regions are more Labour-leaning than the latter, this is the main driver for the relatively larger losses of Labour seats.

Disappearing Seats

For each proposed new seat, we define the predecessor seat to be the old seat which contributes the most voters to that new seat. Old seats which are not the predecessor of any new seat are said to "disappear". This means that they are split into fragments, and none of those fragments forms the largest part of any new seat.

There are 58 disappearing seats across the country, shown in the table below:

If an MP's name is shown here it does not mean that he or she will stop being an MP at the next election. But they have to change the precise area which they represent, and they may be subject to their party's reselection process.

Switching seats

Some new seats have clear predecessor seats, but the boundary changes are large enough that the new seat contains many voters with a different political outlook. This can cause the new seat to have a different predicted party winner from its predecessor. Such seats are called "switching seats", and there are 38 of them:

Notable seats changing hands include the 2019 Conservative victory in Blyth Valley and the 2017 Labour gain in Canterbury, as well as Margaret Becket's seat of Derby South and Tim Farron's seat in Westmorland.

Freshly created new seats

Although the overall change is to reduce the number of seats, there are a few new seats which are freshly created. This means that the new seat is made up of a number of small fragments from various old seats. If the largest component of the new seat is not the largest part of its corresponding old seat, then the seat is defined to be "fresh". There are eight fresh new seats:

England

The Boundary Commission for England published final proposals on 10 September 2018.

The net effect of the changes for England is shown in the following table:

Full details are available on the area pages: North East, North West, Yorks/Humber, West Midlands, East Midlands, Anglia, South West, London, South East

Wales

The Boundary Commission for Wales published final proposals on 10 September 2018.

The net effect of the changes for Wales is shown in the following table:

Visit the Wales Area page for more details.

Scotland

The Boundary Commission for Scotland published its final proposals on 10 September 2018.

The net effect of the changes for Scotland is shown in the following table:

Visit the Scotland Area page for more details.

Northern Ireland

Final proposals for new parliamentary boundaries were published by the Boundary Commission for Northern Ireland on 10 September 2018. Analysis of these final proposals by Electoral Calculus, assuming that 2019 voting patterns remain stable, indicates the the Democratic Unionist Party will lose one seat because two of their existing seats (Antrim South and Lagan Valley) are merged together in the new seat of Antrim South. The total number of seats in the province decreases from 18 to 17.

Visit the Northern Ireland Area page for more details.

History of revisions.

• 30 May 2016 Initial version.
• 9 August 2016 Revised to use projected 2018 boundaries.
• 7 September 2016 Northern Ireland initial proposals included.
• 15 September 2016 England and Wales initial proposals included.
• 19 September 2016 Updated postcode-lookup to show new seats.
• 22 September 2016 Added interactive map information.
• 20 October 2016 Scotland initial proposals included.
• 10 February 2017 Improved calculations of implied results using census demography.
• 28 February 2017 Further small improvements to methodology. Lab takes Brighton North.
• 12 June 2017 Updated for 2017 General Election results.
• 11 September 2017 Updated with news story about possible delay and change to number of seats.
• 18 October 2017 Updated with revised proposals for England, Scotland and Wales.
• 21 February 2018 Updated with revised proposals for Northern Ireland
• 12 September 2018 Updated with final proposals for England, Scotland, Wales and Northern Ireland
• 14 September 2018 Small revisions for multiply-split wards
• 17 October 2018 Updated calculations using more accurate local ward results
• 19 December 2019 Updated for 2019 General Election results.
• 27 April 2020 Updated for announcement of 2023 Boundary Review.

See also the information about the now-abandoned "Sixth Periodic review", to compare against the 2018 Review.