The Prime Minister is braced for the delivery of the Sue Gray report into Downing Street drinking parties during lockdown which could determine his fate.
Many Tory MPs have said they will wait to see the findings before deciding whether to push for a vote of confidence which could see him forced out.
Over the weekend two cabinet ministers – Health Secretary Sajid Javid and Education Secretary Nadhim Zahawi – backed calls by Nusrat Ghani for an inquiry into her treatment.
Ms Ghani said that when she raised the matter with Mr Johnson directly after losing her job in a February 2020 ministerial reshuffle, he told her he could not get involved.
In a sign of the tensions with the party, the Chief Whip Mark Spencer – who admitted speaking to her – angrily denied her claims saying they were “completely false” and “defamatory”.
However, it is Ms Gray’s report – expected later this week – which poses the gravest and most immediate threat to Mr Johnson’s survival in No 10.
The Prime Minister is reported to be determined to hang on to his position believing that he has done nothing wrong.
However, he may be left with little choice depending on exactly what Ms Gray, a senior civil servant, finds.
With widespread public anger and collapsing opinion poll ratings for the Conservatives – and for Mr Johnson in particular – many Tory MPs are in a mutinous mood.
Many of the so-called “red wall” MPs – who took traditional Labour seats in the 2019 – are said to fear they now look set to lose them again in the resulting backlash against the party.
A move against the Prime Minister looked to have been put on hold last week with the defection of Bury South MP Christian Wakeford to Labour, causing MPs to rally to the party colours.
However, the stay may be only temporary with some in No 10 fearing a flurry of letters to the chairman of the backbench 1922 Committee Sir Graham Brady when the report is published.
Under party rules, once the total reaches 54 – 15% of Tory MPs – Sir Graham must call a vote of confidence in the leader.
While Mr Johnson may win such a vote, it would nevertheless be a further body blow to his already diminished authority, raising questions as to how long he could continue.
Among the events, Ms Gray has been investigating is a “bring your own bottle” do in the Downing Street garden in May 2020 during the first lockdown.
Mr Johnson has admitted he was there but said he thought it was a “work event” – an explanation that was met with widespread derision.
She has also been looking at two staff leaving dos on April 16 last year on the eve of the funeral of the Duke of Edinburgh, which have already seen No 10 apologise to Buckingham Palace.
Over the weekend The Sunday Times reported that Ms Gray’s inquiry had been widened to cover claims of parties in Mr Johnson’s Downing Street flat which he shares with his wife, Carrie, and their two children.
Meanwhile, The Daily Telegraph reported Ms Gray has been taking detailed testimony from police guarding Downing Street helping her to build a detailed picture of the comings and goings during lockdown.