Theresa May is considering granting Conservative MPs a free vote on a no-deal Brexit, Jeremy Hunt says, in an apparent bid to avert mass ministerial resignations.

The prime minister faces a walkout if she whips her MPs either for or against crashing out of the EU.

Now the foreign secretary has revealed she is weighing up a free vote on whether to rule out no-deal Brexit – despite inevitable criticism that it would expose her as too weak to impose a collective policy on such a crucial issue.

“That’s something the government has to make a decision on, the prime minister has to make a decision on,” Mr Hunt said. “I don’t think a decision has been taken.”

During an interview, Mr Hunt also confirmed the government could now settle for an “arbitration mechanism” to escape the Irish backstop – rather than demanding a time limit, or strict exit clause.

And he acknowledged an uphill struggle to win the crucial “meaningful vote” next Tuesday, saying: “It isn’t certain – that’s why we have got a lot of work to do.”

The comments came as Geoffrey Cox, the attorney general, and Stephen Barclay, the Brexit secretary, headed to Brussels for talks over the backstop, an insurance policy to avoid a hard border in Ireland.

Britain Before Brexit: Northern Ireland Show all 12 1 /12 Britain Before Brexit: Northern Ireland Britain Before Brexit: Northern Ireland Derry, Londonderry A garage door displaying unionism, bolted shut, like a visual representation of Brexit Britain, locked to outsiders, safeguarding what’s inside Richard Morgan/The Independent Britain Before Brexit: Northern Ireland Derry, Londonderry Rossville Street, the site of Bloody Sunday, where messages demand a severance with England. From this perspective, Britain is England in sheep’s clothing, the real empire, the centre of colonial power Richard Morgan/The Independent Britain Before Brexit: Northern Ireland Bangor A political message in paint not yet dry, still forming, setting, adjusting, or in old paint finally eroding, melting away Richard Morgan/The Independent Britain Before Brexit: Northern Ireland Bangor Moral judgement frames a residential view. The message seeks to make everybody involved in the religious narrative: those who don’t believe are those most in debt Richard Morgan/The Independent Britain Before Brexit: Northern Ireland Castlerock The beach is sparse and almost empty, but covered in footprints. The shower is designed to wash off sand, and a mysterious border cuts a divide through the same sand Richard Morgan/The Independent Britain Before Brexit: Northern Ireland Belfast Two attempts to affect and care for the body. One stimulated by vanity and social norms and narratives of beauty, the other by a need to keep warm in the winter night Richard Morgan/The Independent Britain Before Brexit: Northern Ireland Belfast The gate to an unclaimed piece of land, where nothing is being built, where no project is in the making, where a sign demands the creation of something new Richard Morgan/The Independent Britain Before Brexit: Northern Ireland Derry, Londonderry Under a motorway bridge a woman’s face stares, auburn and red-lipped, her skin tattooed with support for the IRA and a message of hostility to advocates of the Social Investment Fund Richard Morgan/The Independent Britain Before Brexit: Northern Ireland Derry, Londonderry The Fountain Murals, where the curbs and the lampposts are painted the red, white, and blue of the Union Flag. A boy walks past in the same colours, fitting the scene, camouflaged Richard Morgan/The Independent Britain Before Brexit: Northern Ireland Coleraine A public slandering by the football fields, for all to see or ignore. I wonder if it’s for the police or for the community Richard Morgan/The Independent Britain Before Brexit: Northern Ireland Belfast A tattoo parlour, where the artist has downed tools, momentarily, bringing poise to the scene, which looks like a place of mourning, not a site of creation Richard Morgan/The Independent Britain Before Brexit: Northern Ireland Derry, Londonderry A barrier of grey protects the contents of this shop, guarding it from the streets outside, but it cannot conceal it completely, and the colours of lust and desire and temptation cut through Richard Morgan/The Independent

Ms May is pinning her hopes of passing her deal on Mr Cox changing his legal advice that the UK is in danger of being trapped in the backstop – and therefore the EU customs union – indefinitely.

However, the EU has ruled out a time limit or unilateral exit mechanism, forcing the UK to fall back on a much weaker arbitration system.

Brexiteer Tories are demanding the party is whipped to support a no-deal departure if necessary, claiming the support of two cabinet ministers.

“It is crystal clear that the government has to keep no deal on the table and whip against an extension [of Article 50],” former leader Iain Duncan Smith told The Daily Telegraph.

However, that would almost certainly trigger the resignations of Amber Rudd, the work and pensions secretary, David Gauke, the justice secretary, and Greg Clark, the business secretary – who forced Ms May to concede a parliamentary veto on a no-deal Brexit last week.

Speaking to BBC Radio 4, Mr Hunt also softened his previous claim that Britain would thrive after a crash-out Brexit, conceding it “would cause huge disruption”.

And, declining to say the UK was still pushing for a time limit to the backstop, he said: “What we are saying to the EU is that the crucial thing is that, as a sovereign parliament, it must not be possible to trap us in the EU customs union indefinitely.