Conservative MPs vote on Thursday in the first round of a leadership contest, with former foreign secretary and London mayor Boris Johnson the clear frontrunner.
Eighty MPs have publicly endorsed Mr Johnson, more than twice the number backing his closest rival, foreign secretary Jeremy Hunt.
Launching his campaign on Wednesday, Mr Johnson promised to take Britain out of the EU by October 31st, but said he was not seeking a no-deal Brexit, which he described as "a last resort". "Let me be clear that I am not aiming for a no-deal outcome. I don't think that we will end up with any such thing. But it is only responsible to prepare vigorously and seriously for no deal."
MPs rejected a Labour motion aimed at preventing the next prime minister from taking Britain out of the EU without a deal against the will of parliament. The motion, which would have allowed MPs to take control of the parliamentary agenda to legislate against a no-deal Brexit, was defeated by 309 to 298, a majority of 11 votes.
Ten Conservatives supported the motion, but eight Labour MPs defied their party whip to vote against it. The DUP's 10 MPs voted with the government against the motion, but Independent unionist Sylvia Hermon voted in favour of it.
Lady Hermon warned MPs that taking Britain out of the EU without a deal would have “very serious consequences” for Northern Ireland.
“Sinn Féin would certainly be incentivised to campaign for a Border poll were there any hardening of the Border, which would be inevitable with a no-deal Brexit. Heaven help us, but think what dissident republicans might do if there were to be no deal.”
Ten candidates are contesting the Conservative leadership, and MPs will vote in eliminatory secret ballots to choose two to go before the entire party membership. Voting on Thursday will be between 9am and noon, with a result expected at around 1pm. Subsequent ballots are scheduled for next week.
Candidates need to win at least 17 votes to go through to the second round, after which they will need at least 33 votes to proceed to the next round.
Launching his campaign on Wednesday, home secretary Sajid Javid contrasted his background as the son of a Pakistani bus driver with the privileged upbringing of his rivals. Dismissing Mr Johnson as "yesterday's news", he said Conservatives needed a new kind of leadership.
“The problem with much of the Westminster elite, in all parties, is that they have always been insiders, never had to fight like the rest of us just to get their foot in the door.
“Life dealt them a good hand, and they played it – and I can’t blame them for that. But it wasn’t being born to rule or having connections that got me where I am today – it was hard work, public services and my family.”