Philip Hammond has threatened the “fight of a lifetime” if Boris Johnson tries to prevent him from being a Conservative Party candidate at the next election.
The former chancellor is helping lead efforts to block the prime minister from forcing a no-deal Brexit on October 31.
MPs will vote on Tuesday to take control of the parliamentary agenda in order to pass legislation requiring Johnson to delay Brexit until January 31, 2020.
Speaking to BBC Radio 4′s Today programme, Hammond said he believed opposition MPs combined with rebel Tories had the numbers to defeat the government.
“There will be enough people for us to get this over the line to day,” he said.
Downing Street has threatened any Tory MP who votes to block no-deal that they will not be able to stand as the Conservative candidate at the next election.
If the government loses the vote tonight it is expected to call for a snap general election to be held on October 14.
But Hammond has already been reselected as the Conservative candidate by his local Runnymede and Weybridge party.
Hammond, who has been an MP since 1997, said he did not believe No.10 could overrule his local party and threatened to take legal action if it did.
“I don’t believe they do and there would certainly be the fight of al lifetime if they tried to,” he said.“A lot of of my colleagues have come under immense pressure. Some have responded to that pressure by saying enough I am going.
“That is not going to be my approach. This is my party. I have been a member of this party for 45 years. I am going to defend why party against incomers, entryists, who are trying to turn it form a broad church to a narrow faction.”
In what will be seen as an attack on Johnson’s chief aide Dominic Cummings, Hammond said there were people at “the heart of this government who are probably not even members of the Conservative Party, who care nothing about the future of the Conservative Party”.
He added: “I intended to defend my party against them.”
Earlier today Justine Greening, the former Tory education secretary who intends to vote with the rebels, announced she would be stepping down at the next election.
Dominic Grieve, the former attorney general and another rebel, told the BBC this morning he did “not see the Conservative Party surviving in its current form” if the internal battles continued.
For Johnson to hold an election he has to convince MPs to vote for one. And Labour has indicated it will not the plan - because he could use it to ram through a no-deal Brexit.