Cabinet members who oppose a no-deal Brexit have a “duty to resign” if Theresa May fails to abandon the policy, a senior Conservative MP has said.

Dominic Grieve, who backs a Final Say referendum, also branded the idea of crashing out of the EU without an agreement as “committing national suicide”.

At least six cabinet members are known to strongly oppose a no-deal departure, including Philip Hammond, the chancellor, Greg Clark, the business secretary, and Amber Rudd, the work and pensions secretary.

Mr Grieve said the prime minister, after an expected defeat for her deal next week, must immediately pursue an extension of the Article 50 process, while striking the 29 March exit date from domestic legislation.

And, on what should happen if she refused, he added: “If a cabinet minister feels the government is doing something they can’t accept, it is probably their duty to resign.”

“If you can’t take a collective decision to do something, you shouldn’t remain in government.”

David Gauke, the justice secretary, and David Mundell, the Scottish secretary, have also strongly hinted they would resign to stop a no-deal Brexit – while David Lidington, the de-facto deputy prime minister, has warned it could destroy the Union.

A mass cabinet walk-out is seen by some as the most plausible route for stopping a crash-out, if Ms May keeps “running down the clock”, as critics see it.

Mr Grieve said he believed the EU would be willing to stop the clock on Brexit, although Brussels has signalled this might only be for a fresh referendum or a general election.

“I believe the EU will extend Article 50 for us but I think they would only do it in a very limited number of circumstances ... and we need to explore what those circumstances may be,” he told the BBC.

He added: “I hope the prime minister will listen carefully to what members of parliament and members of her own government are saying to her.”

Speaking at an “emergency convention”, in London, to push for a second EU referendum, Mr Grieve predicted defeat for the prime minister’s deal.

“The unpleasant truth for her is that it can satisfy no one,” the former attorney general said.