Ex-cabinet minister David Gauke has warned it is "a fantasy" that the threat of a no-deal Brexit will force the EU to change their position, as the EU's chief negotiator said he was "not optimistic" about avoiding a chaotic departure.
The leading Tory rebel signalled he was prepared to be sacked by Boris Johnson for defying the government next week, saying "the national interest" had to come first.
Mr Gauke confirmed he would meet the prime minister on Monday ahead of a seismic week in the Commons, where rebel MPs will try to wrest control of the Brexit process using legislation.
"I want to hear from him as to what is his plan to deliver a deal," he told Sky News' Sophy Ridge on Sunday.
"When are we putting forward proposals to deal with this backstop issue?
"And, I want to hear how he plans to deliver the legislation if we get a deal by October 31, because at the moment, frankly, I can't see how he's got time to do that."
The prime minister has urged Tory MPs to back him or see Jeremy Corbyn "plunge the country into chaos" amid reports No10 is considering sacking any Conservative MP who votes with opposition MPs this week.
Asked if he would still vote for the bill if it meant being sacked, Mr Gauke said: "Sometimes there is a point where... you have to judge between your own personal interests and the national interest.
"And the national interest has to come first.
"But, I hope it doesn't come to that, and I hope cooler and calmer heads will look at this and think that trying to split the Conservative Party in this way is not a sensible way forward for the Conservative Party, or indeed for the country."
It comes as Michel Barnier, the EU's Brexit chief, poured cold water on the prime minister's claims that there were "signs of progress" in talks with Brussels.
Writing in The Daily Telegraph, Mr Barnier said: "I am not optimistic about avoiding a no-deal scenario, but we should all continue to work with determination.
"On the EU side, we had intense discussions with EU member states on the need to guarantee the integrity of the EU's single market, while keeping that border fully open.
"In this sense, the backstop is the maximum amount of flexibility that the EU can offer to a non-member state."
His refusal to shift on the Irish border backstop casts doubt on the prospect of a new Brexit deal, as the prime minister has described the mechanism as "anti-democratic" and ruled out its inclusion in any agreement.
