But senior Conservatives loyal to the Prime Minister are striving to move on from the party's post-conference turmoil, with Culture Secretary Karen Bradley claiming more than 90% of Tory MPs are in support of Mrs May.
The foreign secretary said "friends and allies" quoted in media reports were not speaking for him and did not represent his views. Johnson, seen as a potential successor to May, said that Conservative lawmakers pushing to unseat her were "nutters", adding that a change would lead to demands for another election that could bring a resurgent Labour party back to power.
One supposed ally told the paper that moving Johnson would go down "like a bucket of cold sick" with pro-Brexit voters, with one saying there was now a "stench of death" from Downing Street.
Claiming the Tories are "in all sorts of trouble" over Brexit, Ms Thornberry added: "It doesn't really matter who their leader is, they don't know where they are going".
"I heartily disagree with the sense, tone and spirit of what they are quoted as saying".
'Whoever they are they do not speak for me'.
Mr Johnson has infuriated his Conservative colleagues by interventions on Brexit that triggered questions of leadership.
Over the weekend, however, pro-Brexit MPs hit back, urging Mrs May to get rid of Philip Hammond, who has argued for a "softer", pro-business Brexit that would protect jobs and investment.
One former minister told City A.M.: "Hammond is safe until the Budget, although of course things are changing fast".
She added: 'I don't think he has been totally on board, I think he has been deliberately trying to make the Brexit negotiations hard, stall them, obfuscate the issues'.
However, Sir Michael Fallon, the Defence Secretary, insisted the Cabinet was united. The reshuffle, according to the Sunday Times, would take place after an October 19-20 summit in Brussels where May will be hoping for a breakthrough few think possible.
But Mr Johnson was backed by environment secretary and arch-Brexiteer Michael Gove, who tweeted: "Strong statement from PM on Brexit - let's be pragmatic over implementation to secure maximum freedom to diverge from European Union in end state". "And somehow that's machinations", Blunt told Sky News.
"He is a big intellect, a big figure in the party and if the Prime Minister believes he is the right person to be Foreign Secretary then she has my full support", she said.