MPs on different sides of the Brexit debate have rubbished claims that Labour MPs could help Boris Johnson get a revised Brexit deal through Parliament.

The prime minister has insisted he can persuade the EU to agree to a "new" deal without the backstop for Northern Ireland. A new deal is very unlikely unless Johnson compromises.

However, even he did secure a new agreement, he would struggle to get it through the House of Commons.

The 25-plus Labour MPs who supposedly could back a Johnson deal are under huge pressure from party members and face deselection if they vote with his government.

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Parliament would almost certainly reject a Brexit deal brought by Boris Johnson, even if he successfully secured a revised agreement with Brussels, as numerous Labour MPs do not plan to back a deal as has been claimed.

The prime minister has described the chances of no-deal Brexit happening as "a million to one" and insisted he can persuade the European Union to change the Withdrawal Agreement by removing the backstop for Northern Ireland.

But that is highly unlikely to happen. The EU has repeatedly said that the backstop will not be removed and Johnson has already ruled potential compromises that Brussels might be willing to consider.

However, even if Johnson was to defy the odds and get the backstop removed, or perform a U-turn and accept a compromise agreement with the EU, he would have little hope of getting it through Parliament.

'How many times have we been here before?'

MPs on different sides of the Brexit debate who spoke to Business Insider have rubbished claims that over 25 Labour MPs could vote for the Brexit deal if Johnson was to put it to another parliamentary vote.

Labour MP Caroline Flint recently said that the 26 Labour MPs who signed a letter to party leader Jeremy Corbyn, urging him to not back a new referendum, could vote for the deal in a new House of Commons vote.

This would be a significant increase on the three Labour MPs who previously voted for Theresa May's deal in the last meaningful vote. Those MPs were Flint, Kevin Barron and John Mann.

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In the run-up to that vote, government sources briefed that a much larger number of Labour MPs were set to back the deal. That speculation was way off the mark, and MPs believe the same thing is happening again.

"How many times have we been here before?" a Labour MP who supports a new referendum told Business Insider.

A number of Labour MPs who Business Insider spoke to made the point that they are about to face trigger ballots, in which local members will decide whether to replace them with other candidates. Labour MPs who vote to support a Johnson deal — and effectively his government — would put themselves at a greater risk of deselection.

This, MPs on all sides believe, makes it fanciful to believe that nearly 30 Labour MPs would vote for a deal with Johnson's name on it, even if they publicly suggest otherwise.

Labour leader Jeremy Corbyn. Dan Kitwood/Getty Images

'Where was the cavalry?'

A senior Conservative MP who was involved in rallying support for May's deal behind the scenes believes that a maximum of eleven Labour MPs could be persuaded to vote for the deal if Johnson brought it back in some form.

However, they suspect the true figure would likely be much lower.

11 Labour MPs would be a significant increase on the three who backed the deal last time — but less than half of the 25 figure which is doing the rounds in Westminster, and way short of what the government would likely need.

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A Conservative MP familiar with the whipping operation told Business Insider: "If there was a cavalry, I can't for the life of me understand why the cavalry didn't come over the hill at the third time of asking, knowing that it would probably lead to a change of Conservative leader and whatever else that might bring.

"It just doesn't make sense. Where was the cavalry? Where was Gareth Snell? Where was Lisa Nandy?

"The general public see their comments, think they want to back a deal, but they never will.

"I think they're getting away with it. They're playing good politics."

Labour MP Lisa Nandy has come close to backing the Brexit deal. Ben Pruchnie/Getty Images

A Labour MP who signed the letter to Corbyn urging him not to back a new referendum said that they would consider backing a revised version of the deal in the unlikely event of Prime Minister Johnson bringing one back.

"I'm not giving Boris carte blanche. He can't bring back any old shit. But ultimately he's going to have to bring back something which has been agreed with the EU," they told Business Insider.

"He keeps saying the deal is dead, but I don't think that line will hold."

However, they said that even 25 Labour MPs behind the deal wouldn't be enough to get it through, as it would be cancelled out by pro-referendum MPs and the "loonies" in the European Research Group of pro-Brexit Conservatives.

Even if Johnson was to prove the "doomsters" and "gloomsters" wrong by securing a new Brexit deal from EU leaders, as things stand, he would have very little chance of getting it through the House of Commons.