Philip Hammond has suggested he is prepared to vote to bring down a Boris Johnson government should the likely new prime minister push for a no-deal Brexit.

In an outspoken intervention days before Johnson is expected to win the keys to Downing Street, the chancellor said it was “absolutely necessary” for the UK to extend its EU membership beyond 31 October.

Asked whether he would rule out voting in favour of a no-confidence motion against Johnson, Hammond told Le Monde and Süddeutsche Zeitung: “I will take steps to avoid an exit without agreement apart from an explicit parliamentary approval.

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“There should be a new and sincere attempt to reach a consensus. If we do not find a solution with the members, we may have to ask the British to give their opinion again, in one form or another.”

Asked again to rule out supporting a motion of no confidence, Hammond responded: “I do not exclude anything for the moment.”

The chancellor was one of four cabinet ministers who broke ranks with the government to abstain on a vote on Thursday, the result of which prevents Johnson from proroguing, or suspending, parliament in order to push through an exit from the EU without a deal.

He also reportedly encouraged others to vote to ensure that parliament continues to sit through September and October.

In his interview with the two media outlets, Hammond said he could not see any prospect of a successful negotiation with the EU before 31 October, when Johnson says the UK will leave, “do or die”.

He added that he did not think it a good idea to continue endlessly extending the UK’s membership of the EU to avoid no deal, but could not accept the economic damage that would be inflicted on leaving this autumn. The Office of Budget Responsibility warned this week that a no-deal Brexit would require an additional £30bn in government borrowing.

Hammond said: “In practice, extending the deadline is absolutely necessary. Between the summer break, the arrival of the new commission and the change of the British government, it is simply impossible to negotiate anything before October 31.

“If the next government is sincere in its desire to reach an agreement with Europe, it must try to get more time. If it does not, the British parliament will insist on getting a new postponement.

“I will remain a member of the House of Commons. I will do everything in my power from my position to make sure that parliament blocks a Brexit without agreement.”

There is little love lost between Johnson, a former foreign secretary, and the chancellor, who has despaired at the spending promises made by the leadership hopefuls and has refused to endorse either of the candidates.

“He is actually a more complex personality than it sometimes seems,” Hammond said of Johnson in his interview. “He is a mainstream conservative on all topics except Brexit. I very much regret his attitude to Brexit. His own story, which is multicultural, multinational and liberal, speaks for itself.”

But Hammond admitted he could understand the frustration in EU capitals at the state of the Brexit process “because some of my compatriots are deliberately noisy, rude and inconsiderate”.

“Some are trying to make the Europeans so tired that they ask us to leave,” he said. “But please, do not listen to the the few noise-makers.”

Hammond said that the expected exodus of companies from the UK had not yet happened but that he feared for a future in which the EU’s member states would “have the power” to establish heavy controls on UK goods coming to the continent.

“I hope there will be intense competition between European ports,” Hammond said. “I believe that the Belgian and Dutch ports are preparing for a fierce competition to take advantage of this commercial traffic.”

In the financial sector, the chancellor said there had yet to be an exodus from the City of London.

He said: “Some banks have moved a handful of their staff to the EU to deal with the situation. My concern is more about what will happen in a year or two if we do not reach an agreement with the Europeans. In this case, the European authorities will demand that risk control be strengthened and more capital relocated to the continent.

“For the rest, I am surprised that there is no debate in Europe about the risk that a large financial sector represents for taxpayers.

“In the United Kingdom, they had to pay £180bn to avoid the bankruptcy of the banks in 2008 and 2009. Do the Europeans really want to assume such a burden?”

Hammond added that the dropping away of financial activity in the City “could be a slow process”. “But it is not certain that this would benefit Paris or Frankfurt,” he said. “It is equally likely that US banks will repatriate their employees to New York and serve the European market from there.”

