Prime Minister Theresa May’s Brexit talks with the Labour Party are a “grave mistake”, according to former defence secretary Gavin Williamson.
Mrs May is hoping to reach a cross-party consensus on her withdrawal agreement after failing to get it through Parliament three times.
He added Jeremy Corbyn’s only real interest was a general election.
BBC political correspondent Jonathan Blake said a Downing Street source had indicated Mr Williamson had been “supportive of the process while he was in the cabinet” and that he had “not been involved in the talks himself”.
The Conservative MP for South Staffordshire said doing a deal with Labour on Brexit “sounds so simple and so reasonable” – but would not work.
“Even if Labour do a deal, break bread with the prime minister and announce that both parties have reached an agreement, it can only ever end in tears,” he said.
“The Labour Party does not exist to help the Conservative Party.
“Jeremy Corbyn will do all he can to divide, disrupt and frustrate the Conservatives in the hope of bringing down the government.
“His goal, and he has made no secret of it, is to bring about a general election.”
Mr Williamson said the prime minister seemed oblivious to the fact many Tories believe she is “negotiating with the enemy”.
He continued: “Even if we get to a point where Jeremy Corbyn agrees a deal with the prime minister, when it comes to detailed scrutiny of the votes, Labour will revert to form.
“Even if it passes the first few votes, it will fail later.”
The UK had been due to leave the EU on 29 March, but the deadline was pushed back to 31 October after Parliament was unable to agree a way forward.
Mr Williamson was sacked as defence secretary following an inquiry into a leak from a top-level National Security Council meeting.
Downing Street said the PM had “lost confidence in his ability to serve” and announced Penny Mordaunt as his successor.
The inquiry came after details of a discussion by the NSC over a plan to allow Chinese tech firm Huawei limited access to help build the UK’s new 5G network was leaked to a newspaper.
Mr Williamson, who was defence secretary between 2017 and 2019, “strenuously” denied leaking the information.