Boris Johnson will "just say no" if Theresa May tries to demote him, his allies have said as they warned sacking him as Foreign Secretary would undermine Brexit and destabilise the Government.

The Prime Minister is instead being urged by members of her Cabinet to sack Philip Hammond, the Chancellor, for "making Brexit hard" and being "miserable".

Mrs May indicated that Mr Johnson could be moved into another Cabinet role in a reshuffle at the end of the month, saying that she would not "hide from a challenge".

Her comments prompted a furious response from Mr Johnson's backers, with one Tory minister saying that there is a "stench of death" emanating from Downing Street.

They warned that the Prime Minister lacks the authority to demote Mr Johnson in the wake of her disastrous General Election performance and chaotic conference speech.

Running man: Foreign Secretary Boris Johnson, out for his Monday morning jog, remains a looming presence in Theresa May's Cabinet credit: Carl Court/Getty Images

One ally said that removing Mr Johnson as Foreign Secretary would go down "like a bucket of cold sick" with Brexit voters amid concerns that key Cabinet roles are dominated by Remain campaigners.

Even a minister who is critical of Mr Johnson's recent interventions told The Telegraph that removing him would "undermine public confidence in Brexit".

Eurosceptic Tory MPs publicly turned on Mr Hammond, saying that he should be demoted instead for "deliberately trying to make Brexit negotiations difficult".

They were backed by a Cabinet minister, who said : " He has completely failed. He has not given her any domestic announcements that she can sell. He is miserable, he talks people down, he is making Brexit hard. He just saps everyone's self-confidence."

An ally of Mr Hammond said: "The Chancellor has made very clear that we're leaving the Customs Union and Single Market when we leave the European Union in March 2019. He is not trying to frustrate the process at all."

The Prime Minister is attempting to re-assert her authority after Downing Street saw off a coup by around 30 Tory MPs who want her out by Christmas.

It follows a calamitous speech at the Conservative Party conference in which she was handed a P45 by a prankster, lost her voice and the stage behind her fell down.

The Prime Minister is now considering a reshuffle at the end of the month to ensure that she has "the best people in my Cabinet".

Asked about Mr Johnson's future, she told The Sunday Times: “It has never been my style to hide from a challenge and I’m not going to start now."

Several Cabinet ministers have made it clear that Mrs May would have their support if she removed the Foreign Secretary, who they blame for “destabilising” the party.

Mr Johnson has been accused of “disloyalty” over his decision to announce a series of Brexit "red lines" on the eve of the Conservative Party conference, including warning that the transition period should not last "a second longer" than two years.

However Mr Johnson's allies said that removing him would be "insane". One Tory minister highlighted Andrea Leadsom, who threatened to resign after being axed as Environment Secretary.

After a stand-off with Mrs May she was offered a high-profile media role in promoting and defending the Government alongside her position as Leader of the Commons.

The minister said: "Let's say she tries to move Boris to defence secretary. Leadsom said no thank you, and Boris carries significantly more influence. He'd just say no - what is she going to do about it?

"There's a stench of death emanating from Downing Street. If you were a Brexiteer you would be worried [if Mr Johnson was demoted]. You'd look around the Cabinet table and see Remainers occupying the key positions."

Another minister said: "Brexit is absolutely crucial to democracy in this country now. If we fail to deliver that the public will never forgive us. A reshuffle would be a huge distraction, we don't need to replace people for the hell of it.

"It [removing Mr Johnson] will undermine public confidence in Brexit. It would be counter-productive."

Lord Heseltine, a former Deputy Prime Minister, also suggested that Mrs May would be taking a "high-risk" gamble if she sacks Mr Johnson.

He said: "I think that if she wants to assert her authority she would have to sack him, but of course it's a high-risk policy because he will be on the back benches and he won't go quietly."

Nadine Dorries, a eurosceptic Conservative MP, said Mr Hammond should be sacked instead. She said: “If I were the Prime Minister the person I would be demoting, or certainly sacking, would be Philip Hammond.

"I think he's been deliberately trying to make the Brexit negotiations difficult, stall them, obfuscate the issues. I just don't think he's been absolutely 100 per cent on board."