Brexit: 40 government ministers could resign unless they can vote against no-deal, Theresa May warned

Amber Rudd leads calls for Tory MPs to be given free vote on key backbench motion to extend Article 50 if no agreement in place next month

Theresa May has been warned that up to 40 government ministers could resign if she refuses to allow them to vote for a plan that would block a no-deal Brexit in March.

Amber Rudd, the work and pensions secretary, has told No10 it faces an exodus of members of the government unless ministers are allowed to support a backbench amendment that would extend Article 50 if a Brexit deal is not in place within weeks.

The amendment, tabled by Labour’s Yvette Cooper and former Tory ministers Sir Oliver Letwin and Nick Boles, will be debated and voted on by the Commons on 29 January.

Ms Rudd is urging Ms May to give Tory MPs a free vote on the motion in order to avoid a mass ministerial walkout.

One Conservative MP told The Times: “Amber is telling Downing Street to make it a free vote on behalf of lots of people.”

Ms Rudd's spokesman declined to comment.

Ms May's cabinet is heavily split on Brexit, with pro-Europe ministers including Ms Rudd, chancellor Philip Hammond and business secretary Greg Clark urging her to rule out a no-deal withdrawal and pursue a softer exit strategy.

The prime minister has repeatedly refused to rule out no deal, saying doing so is "impossible".

The amendment tabled by Ms Cooper would force the government to ask the EU to delay Brexit until the end of the year if no deal is in place by the end of February.

It is the latest version of a plan devised by a cross-party group of senior backbenchers who want to block a no-deal Brexit.

An earlier proposal would have seen control of Brexit handed to the powerful Commons Liaison Committee if the government was unable to secure parliamentary support for its deal, but that idea was dropped after members of the committee, which is made up of the heads of all the other Commons committees, voiced concerns.

Labour has hinted it will back the latest plan, along with enough Tory rebels to allow it to pass.

Asked about the proposal while answering questions from MPs in the Commons, Ms May insisted the only way to guarantee there is not a no-deal Brexit is to revoke Article 50 entirely - a move she said "would go against the referendum result".

She said: “There is widespread concern about the possibility of the UK leaving without a deal. And there are those on both sides of the House who want the government to rule this out.

“But we need to be honest with the British people about what that means. The right way to rule out no deal is for this House to approve a deal with the European Union. That is what this government is seeking to achieve.”

She continued: “The only other guaranteed way to avoid a no-deal Brexit is to revoke Article 50, which would mean staying in the EU.

“There are others who think that what we need is more time, so they say we should extend Article 50 to give longer for parliament to debate how we should leave and what a deal should look like. This is not ruling out no deal, but simply deferring the point of decision. And the EU are very unlikely simply to agree to extend Article 50 without a plan for how we are going approve a deal.

“So when people say ‘rule out no deal’ the consequences of what they are actually saying are that if we in parliament can’t approve a deal we should revoke Article 50. I believe this would go against the referendum result and I do not believe that is a course of action that we should take, or which this House should support.”