A £2.5 million review of England’s electoral map is due to be published next week, in a shake-up that could see a controversial “Devon-wall” seat created.

Under proposals to make voter populations in each constituency more equal, England is set to gain 10 MPs, while Wales will lose eight and Scotland is on course to be reduced by two.

But even with the gains, the Boundary Commission for England, which is due to publish its initial recommendations on Tuesday before a consultation takes place, said a seat merging areas of Cornwall and Devon could not be ruled out.

Ultimately we have to get every constituency between the 69,000 and 77,000 figure and if that means we have to cross a barrier such as the River Tamar, then unfortunately that is something the commission may have to do

The concept met local opposition on both sides of the historic boundary in the south-west of England when proposed in former boundary reviews.

Tim Bowden, secretary to the English commission, told reporters on Wednesday: “You could see a constituency that straddles the River Tamar between Devon and Cornwall.

“We try the best that we can to reflect those natural and man-made features in terms of rivers, motorways, railways, etc.

“However, ultimately we have to get every constituency between the 69,000 and 77,000 figure, and if that means we have to cross a barrier such as the River Tamar, then unfortunately that is something the commission may have to do.”

Although the overall number of UK parliament constituencies will remain at 650 as part of the overhaul, population changes mean England is set to have 543 MPs, Wales 32 and Scotland 57 – a net gain of 10 for England, with Wales losing eight and Scotland having two shaved off.

Northern Ireland will continue to have 18 MPs in the House of Commons, but some of the current boundaries could shift as part of the plans, according to the region’s boundary commission.

In January, the Office for National Statistics (ONS) published the voter data on which the review will be based, with 47.5 million voters to be divided into 650 constituencies of between 69,724 and 77,062 people in size.

Some island constituencies, such as the Isle of Wight and the Isle of Anglesey, have been granted special dispensation to be outside the population remit.

Currently, UK constituencies range from 50,000 to 100,000 in size and Mr Bowden said one of the benefits of the review would include ensuring every MP represents “roughly the same number of electors in their constituency”.

Mr Bowden said the review, with final proposals due to be submitted in July 2023, in time to be used for the 2024 general election, were projected to cost £2.5 million.

“I believe the 2018 review cost approximately £5 million, so it is quite a significant shift in terms of our total costs that we are predicting to come out at,” he added.

“That’s been done either through efficiency savings or learning from what we’ve done over previous reviews and being able to be more efficient and effective in how we use public money ultimately.”

The work of the commission will continue even in the event of a snap general election being called before 2024, he added.

Plans proposed by former prime minister David Cameron’s government to cut the number of MPs by 50 while also making constituency populations more equal were ditched by Boris Johnson’s administration last year.

A review in 2013 went unfinished, while proposals in 2018 were laid aside.