The Chancellor declared: “I would do everything in my power from my position to make sure that Parliament blocks a Brexit without agreement.”
Asked if he would go as far as to vote for a no- confidence motion against the new prime minister, he replied: “I do not exclude anything for the moment.”
The defiant signal was made in an interview with French paper Le Monde and a German daily. Mr Hammond, who is emerging as the leader of Conservatives opposed to a no deal, said it was “absolutely necessary” to delay Brexit from October 31.
He said Parliament will “insist on getting a new postponement” if the new government failed to ask for one.
Calling for “a new and sincere attempt to reach a consensus”, he said a new referendum or a general election would be needed if none was found.
The Evening Standard learned today that senior Conservatives have moved to protect Mr Johnson from being toppled as leader for at least a year.
Party rules were “clarified” at a meeting of the executive of the 1922 Committee of Tory backbenchers to bar any confidence vote being staged in the next prime minister until at least July 23, 2020.
But with just five days until Mr Johnson is expected to enter No 10 as PM, the Tories seemed to be heading for civil war.
Health minister Stephen Hammond, one of 36 Conservative rebels who yesterday voted against any suspension of the Commons to force a no-deal Brexit, also hinted he might back a no-confidence vote.
His intervention was branded “puke making” by fellow Tory MP and Brexiteer Michael Fabricant.
Wimbledon MP Mr Hammond said it was time for MPs to “do the right thing” and put country before personal ambition. “I hope we never get there but I think a lot of people were taught that you must put the interest of the country before yourself,” he told BBC Radio 4’s Today programme.
Asked if he was personally prepared to press the “nuclear button” of a no-confidence vote, he said he would be “very, very, very cautious about ever doing that. I’m a Conservative through and through and no one takes any pleasure in rebelling.”
But he continued: “I think it’s really important that, at this historic stage in this country’s lifetime in modern politics, politicians put aside any of their own personal ambitions or views and actually make sure they do the right thing as they see it for the country.”
Opposition parties have said they would stage a confidence vote in October if it was the only way to stop Mr Johnson carrying out his “Plan C” of crashing out on October 31 if the EU denies him a better deal.