Philip Hammond warns he could bring down the UK government if the new prime minister attempts a no-deal Brexit

Chancellor Philip Hammond warns the next Conservative leader that MPs could bring down the government if they pursue a no-deal Brexit.

The early stages of the Tory leadership contest have been dominated by each candidate's proposal to break the Brexit deadlock.

Conservative party grandee Michael Heseltine warned on Wednesday evening that voters would say “goodbye and good luck” to the Conservatives if they pursue a no-deal Brexit.

The EU's chief Brexit negotiator Michel Barnier again warned that Theresa May's Brexit deal could not be renegotiated.

LONDON — Chancellor Philip Hammond has warned those competing to replace Theresa May that he could bring down the next leader of the UK government if they attempt to pursue a no-deal Brexit.

The chancellor, a vocal advocate for a soft EU exit, suggested he could vote for a motion of no confidence in the government, if any new Conservative leader advocated leaving the EU without a deal.

“I have been in parliament for 22 years and I have never once voted against the Conservative whip so it's not something I would do lightly or enthusiastically, but I am very clear that the national interest trumps the party interest, and if I am presented with a difficult choice I will act in what I believe is the best interest of the country,” Hammond told Sky News on Thursday.

Theresa May is set to leave Downing Street in July and be replaced by a new Conservative prime minister.

Many of the leading frontrunners for the leadership, including former Cabinet ministers Boris Johnson and Dominic Raab, have suggested the UK must leave the EU by October 31, with or without a Withdrawal Agreement.

The chancellor's comments echo those of Foreign Secretary Jeremy Hunt, who warned this week that a no-deal Brexit would be “political suicide” for the Tories because it would prompt a vote of no confidence in the government, which could ultimately install Jeremy Corbyn in Downing Street.

The early stages of the leadership contest — in which 11 MPs have already put their name forward — have been dominated by each candidate's plan to resolve the Brexit gridlock.

Some, including Jeremy Hunt, have pledged to renegotiate Theresa May's withdrawal agreement with the EU rather than pursue no-deal, but negotiators in Brussels have repeatedly insisted such an option is not on the table.

The EU's chief Brexit negotiator Michel Barnier repeated on Wednesday that parliament had a choice between approving May's deal, revoking Article 50, or leaving with no deal at all.

He told The New York Review of Books: There are three options: a deal based on the agreement finalized six months ago; withdrawal without a deal; or no Brexit.

“It will have to be the choice of the UK. During the last three years, we have delivered what the UK wants: leaving the EU, leaving the single market, leaving the customs union [after the Irish ”backstop“ is resolved] ... if the UK wants to leave in an orderly manner, this treaty is the only option.”

'Goodbye and good luck' to the Conservative party

Tory grandee Michael Heseltine also warned on Wednesday evening that voters would say “goodbye and good luck” to the Conservatives if they pursue a no-deal Brexit.

The former deputy prime minister, who advocates a second EU referendum, said the party risked being caputured by the “narrow nationalism, phobia-filled and poisonous politics of Nigel Farage.”

Farage's Brexit Party won the most seats in last week's European elections while the Conservatives plummeted to fifth with 9% of the vote. Some Conservative MPs have interpreted the result as evidence that the party should adopt a harder stance on Brexit and pursue a no-deal Brexit as official government policy.

Watch Philip Hammond threaten to collapse the government

The hopes of no-deal Brexit supporters were also dealt a blow this week by John Bercow's announcement that he would stay on as House of Commons speaker instead of standing down in July, as had been widely expected.

The speaker — who Brexit-supporting MPs have frequently accused of a Remain bias — warned leadership candidates that they would not be able to take Britain out of the EU with no deal if parliament opposed it.

“The House will want to have its say and the idea the House won't have its say is just for the birds,” Bercow said in a speech in Washington on Tuesday.

'The idea that there is an inevitability of a no-deal Brexit would be quite a wrong suggestion, he said.