Boris Johnson has vowed to fire cabinet ministers opposed to a no-deal Brexit, a stance likely to trigger the sackings of David Lidington and Amber Rudd.

Only ministers “reconciled” to crashing out of the EU on by the current deadline of Halloween if necessary will be allowed to stay on, the Tory leadership favourite said.

Asked if every cabinet member would have to be “committed to leaving on 31 October, deal or no deal”, Mr Johnson replied: “Yes, that will be the policy of the government.”

And he added: “Clearly, people must be reconciled to the very, very, very small possibility, and I stress it will be a very, very small possibility, that we would have to leave on those terms [a no deal].”

Both Ms Rudd, the work and pensions secretary, and Mr Lidington, the de facto deputy prime minister – as well as the justice secretary David Gauke and the business secretary Greg Clark – are outright no-deal opponents.

Ms Rudd was touted as a possible chancellor under Mr Johnson but backed rival Jeremy Hunt instead, because of Mr Johnson’s willingness to crash out with no agreement.

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However, in the interview with the Conservative Home website, Mr Johnson did leave wriggle room when asked if he would defy an order by MPs to seek a further Article 50 extension.

It was exactly such legislation that compelled Theresa May to delay Brexit in March – and anti-Brexit MPs are certain to try to pass a fresh law in the autumn.

That effort will start next week, with a cross-party amendment to deny essential funding to key departments if the UK leaves without a deal, without parliament’s specific approval.

Mr Johnson was asked if he was saying that, even if MPs voted for an extension, “you will not go and seek an extension, because we must leave on 31 October”.

But he replied: “I’m not quite saying that” – arguing that conflict would not arise because “the parliamentary mood has changed and continues to change”.

The comments came as Mr Lidington underlined his opposition to a no deal when asked if he would join a vote of no confidence in the Commons to block it.

“I’m not in the business of wanting to put Jeremy Corbyn into government, because I think that would be disastrous for the country on both economic and security grounds, but I am very opposed to no deal,” he replied.

He added: “I believe we should follow the referendum result and leave with a deal and then use the implementation period to negotiate a very close partnership with the European Union.”

Mr Gauke has said he could not serve in Mr Johnson’s cabinet if he continued on his “do or die” Brexit course.