Boris Johnson has hit out at "so-called friends and allies" in a Whatsapp rant amid speculation that he would refuse to go if he was demoted in a cabinet reshuffle.
In the message to Conservative MPs, the Foreign Secretary said he was "fed up to the back teeth" with the claims.
It follows reports in The Sun and The Telegraph, with the latter quoting one backer of Mr Johnson as saying that there was a "stench of death" emanating from Downing Street.
The message, which has been posted on social media, read: "I do not know who these people are.
"I do not know if they are really my friends and allies or if they represent some sinister band of imposters.
"I heartily disagree with the sense, tone and spirit of what they are quoted as saying."
Prime Minister Theresa May has faced repeated calls from Tory MPs to sack Mr Johnson after he set out his own "red lines" on the Brexit negotiations in defiance of Government policy.
However over the weekend, pro-Brexit MPs hit back, urging Mrs May to get rid of Chancellor Philip Hammond, who has argued for a "softer", pro-business Brexit that would protect jobs and investment.
An unnamed Cabinet minister told the Telegraph that Mr Hammond had "completely failed", was "miserable" and was "making Brexit hard".
Tory MP Nadine Dorries was more direct, telling ITV's Peston on Sunday: "If I were Prime Minister the person I would be demoting or sacking would be Philip Hammond. I think she very much wanted to do that before the election was called.
"I don't think he has been totally on board, I think he has been deliberately trying to make the Brexit negotiations difficult, stall them, obfuscate the issues. I just don't think he has been 100% on board."
Theresa May's official spokesman declined to comment on reshuffle speculation, but said that the Prime Minister has full confidence in both Mr Hammond and Mr Johnson and believes both are doing a good job.
Asked if Mrs May agreed with Eurosceptic Tories that the Treasury was blocking progress on Brexit, the spokesman said: "The Treasury, like every department in Whitehall, is working hard to deliver on the wishes of the British public and to deliver a smooth and orderly Brexit."
He added: "I never discuss whether reshuffles are or are not taking place. But as the Prime Minister said yesterday in the Sunday Times, she has a fantastic Cabinet."
The spokesman was asked whether Mrs May's response to a question about Mr Johnson in the Sunday Times interview, when she said that she did not "duck challenges", meant that she regarded her Foreign Secretary as a "challenge".
He responded: "The PM was talking broadly about how she is a politician who never ducks a challenge."