Labour is likely to be hit hardest by changes to parliamentary boundaries, potentially losing 30 seats altogether.
Two hundreds Labour seats could be affected by plans to cut the number of Westminster constituencies, new analysis has found.
The boundary review will see the number of MPs in the Commons reduced from 650 to 600.
Analysis by election expert and Tory peer Lord Hayward indicated that Labour will “suffer most” as a result of the proposals - leading to claims of “gerrymandering” from the Opposition.
The boundary review, set to come into effect in time for the 2020 general election, is an attempt to reduce the size of the Commons and create seats with similar numbers of constituents.
The Boundary Commissions for England, Wales, Scotland and Northern Ireland are due to publish their proposals for the new constituencies during September.
Ahead of their official publication, Lord Hayward’s analysis suggests that although most seats will be affected by the changes, Labour looks set to lose more MPs than the Conservatives as a result of the shake-up.
“The party that will suffer most is the Labour party because such a high proportion of their current seats are well below the required quota, particularly in Wales, the north-east and parts of the M62 corridor,” Lord Hayward told The Guardian.
The impact on Labour could be especially painful, as critics of Jeremy Corbyn face the prospect of reselection processes for the revised constituencies.
“This will have implications for large numbers of Labour MPs who may well have to compete against each other for reselection,” Lord Hayward said.
The number of registered voters in each constituency to within 5% of 74,769. A higher proportion of Tory seats are currently within the range, so only between 10 and 15 of the party’s seats are expected to disappear, the analysis indicates.
Lord Hayward’s figures suggest that of the 50 seats that disappear, the Conservatives will lose between 10 to 15, which is 4.5% of their total but Labour is on track to lose between 25 and 30, some 13% of their current representation.
Some constituencies could turn from safe Labour seats to marginal ones, while other parties, including the SNP, will also be hit.
Labour’s work on the boundary review has been led by Dame Rosie Winterton, the chief whip, and her spokesman said the analysis was fresh evidence the policy was a “partisan” move to benefit the Tories.
The Opposition urged Prime Minister Theresa May to abandon the plan, arguing that the imminent loss of 73 MEPs as a result of Brexit would heap extra work on MPs.
Labour also highlighted the surge in numbers on the electoral roll as a result of the EU referendum, resulting in an extra two million registered voters who were not factored in to the boundary review.
“The Tories’ plan to arbitrarily reduce the number of elected Members of Parliament by 50 had always been under the guise of reducing the cost of politics, even whilst they continued to cram the Lords at taxpayers’ expense,” Dame Rosie’s spokesman said.
“Lord Hayward’s comments - a key architect of the Conservative’s boundary changes - that reducing the number of elected Members of Parliament by 50 will benefit the Tories’ electorally, is further evidence that the sole motivation for these changes is a partisan plan to give the Tories an unfair advantage at the expense of democracy.
“Simply put this is gerrymandering.”