They have sworn a pledge to keep Britain in the EU after publicly insisting they would respect the referendum result.

About 40 wannabe MPs are standing in seats where a majority of people voted to leave the EU.

But despite previous vocal support for getting Brexit done, they have all signed the Remainer pledge to sell their prospective constituents down the river.

The great betrayal will undermine leader Jeremy Corbyn’s big push to woo back Leave voters in Labour heartlands where support is crumbling.

One worried party insider said: “These areas are overwhelmingly in favour of Brexit but those who want to be their Labour MPs are sworn to blocking it. Despite what some of them think, Leave voters aren’t stupid and will see through their attempts to hoodwink them.”

Sixteen of the 40 are Labour MPs seeking re-election, having defied voters in the past three years by voting to block, delay and derail Brexit on numerous occasions.

Eight are in very heavy Leave areas where up to 73 per cent backed Brexit.

They include high-profile figures such as the former Foreign Secretary Margaret Beckett, ex-minister Chris Bryant and former shadow Cabinet member Mary Creagh.

LABOUR HOPEFULS: 'I PLEDGE TO REMAIN IN THE EU'

In total, 182 General Election candidates have signed a pledge drawn up by the campaign group Remain Labour.

It states: “Labour is committed to a confirmatory referendum, to give you the final say on Brexit. If elected as your Labour MP, I pledge to campaign to Remain in the EU.”

By contrast, all 635 Tory candidates have promised to vote in favour of Boris Johnson’s Brexit deal.

But many Labour hopefuls appear to be going back on their word to deliver the will of the people.

Mrs Beckett, defending her Derby South seat where 61.4 per cent voted Leave, had previously insisted she accepted the decision her constituents had made. She declared in May 2017: “We have to make the best of it.”

Another, Anna Turley -seeking re-election in Redcar where 67.7 per cent voted for Brexit -had said: “I will fight for a Brexit that is fair for Teesside”.

Wakefield MP Ms Creagh, who declared before the referendum “if we vote to leave, there’s no going back”, is now of the firm belief there is.

Jess Phillips has also signed the Remain Pledge despite assuring Birmingham Yardley voters in 2017: “Sixty-odd per cent of constituents want us to leave. I cannot ignore that.”

Labour campaign chiefs will this week launch a last-ditch blitz of “Red Wall” Leave-voting constituencies amid evidence working classes are rallying behind Boris Johnson to save Brexit.

They face losing a swathe of seats in the north Midlands and Wales, with the biggest swing to Tories in Leave areas.

Labour support in Grimsby, held by the party since 1945, has now collapsed dramatically from 49 per cent in 2017 to just 31 per cent.

DOUBLE-CROSSING THE 17.4million

Tony Blair’s former seat of Sedgefield, which has not had a Tory MP since 1935, is on BoJo’s target list.

An overwhelming 59.4 per cent there voted to Leave and sitting MP Phil Wilson said in 2017: “We respect their decisions and voted accordingly in Parliament in favour of Article 50.” Yet he has since put his name to the “Remain Pledge”.

Ilford North’s Wes Streeting has also changed his stance since he said: “I voted to give the people a choice and I will abide by their decision.” Many Labour candidates who have not signed the pledge have barely tried to hide their derision for Leave voters.

Sonya Ward, standing in Mansfield, mocked the 70.86 per cent who voted Leave there by claiming they “got it wrong, because they didn’t understand”.

Tory chairman James Cleverly said last night: “This is a damning indictment of the very people these candidates want to represent, as well as the 17.4million people who voted to leave in 2016.

“Despite pledging to respect the result of the referendum, Labour candidates have turned their backs on Brexit in favour of backing a second referendum and stopping Brexit altogether.”

Former Labour leader Ed Miliband, defending the Brexit hotbed of Doncaster North, has not signed the pledge.

He has been telling his constituents, 72 per cent Leave, that he voted for a Brexit deal nine times -but Tories pointed out he voted down Theresa May’s and Boris Johnson’s.

His double-dealing exposes the scale of panic in Labour’s northern heartlands.

Left-wing activist Owen Jones woke up to the Brexit backlash last week, admitting: “If Labour doesn’t do more to win back Leave voters in the North, Midlands and Wales, then Boris Johnson will win a majority.”