An imminent shake-up of the UK’s constituency borders will give the ruling Conservative party up to 10 more seats at the next general election, according to experts.
The government in December passed the Parliamentary Constituencies Act, under which all 650 seats across the country will be redrawn to give them a similar number of voters — about 73,000.
The boundary changes represent a fresh challenge for the opposition Labour party, which needs to gain at least 124 seats to secure a majority at the next election, expected in 2024.
Reviews of parliamentary constituencies are carried out by independent commissions for England, Wales, Scotland and Northern Ireland. Current boundaries are based on data from 20 years ago and the government says that the updated borders will reflect “significant changes in demographics, house building and migration”. The last changes took place in 2010 and were based on data from 2000.
In 2011 parliament approved plans to cut the number of MPs and equalise constituency sizes but these were abandoned in 2013 after the Liberal Democrats joined the opposition to vote against their Tory coalition partners. Another attempt failed in 2018 when Theresa May lost her majority in the Commons.
Boris Johnson, the prime minister, has dropped plans to reduce the number of MPs but is pressing ahead with equalising constituency populations.
New figures to be released by the Office for National Statistics on January 5 will confirm the size of the electorate in March 2020 and will trigger the start of the Boundary Commissions’ new review. Its final reports will be presented to the speaker of the Commons by July 1, 2023.
The borders of every seat in the UK will be redrawn to ensure the number of voters is more or less equal, with the exception of five “protected constituencies”: Ynys Mon in Wales, and Orkney & Shetland and Na h-Eileanan in Scotland will each retain one MP, while the Isle of Wight will be split into two seats.
Each constituency’s population can be up to 5 per cent larger or smaller than the 73,000 target.
Martin Baxter, founder of Electoral Calculus, a psephology website, said the changes were the “fair thing to do” given current imbalance between the size of seats.
“My own algorithm suggests the Conservatives will do a bit better than Labour by about 10 seats,” he said. “It’s equivalent to a swing of 1 per cent from Labour to the Conservatives, in political terms that’s not nothing.”
Robert Hayward, a veteran Tory psephologist, said he thought the redrawn map would help his party by five to 10 seats.
Lord Hayward estimates that the most affected areas will include Wales, which will lose about eight MPs, while Scotland, north-east England, the West Midlands, Yorkshire & Humber and north-west England will each lose one or two.
London — which is heavily skewed towards Labour — could gain a few seats. But the overwhelmingly Tory areas of south-east and south-west England are expected to gain seven and three MPs respectively.
The Parliamentary Constituencies Act has also raised the national campaign spending cap at the next election from £19.5m to about £33m. That change is expected to benefit the Tory party, which tends to attract financial backers with deeper pockets.
Meanwhile, Mr Johnson is set to scrap the Fixed Term Parliament Act, giving the incumbent administration the power to decide the timing of the next election instead of being required to hold one every five years.