A one-time ally of Boris Johnson has accused him of “unacceptable failures of leadership” in a fresh blow to his battered authority.
The Prime Minister faces the threat of a no confidence vote as soon as next week amid growing dismay among Tory MPs over his premiership.
Mr Johnson is trying to brazen out the findings of Sue Gray's bombshell Partygate report, which laid bare the extent of lockdown boozing in Downing Street during the pandemic.
But a steady stream of Tory MPs have broken cover to express their fury at the Prime Minister since the publication of the report..
In a major blow, former Cabinet Minister Andrea Leadsom told constituents that she agreed with Ms Gray that report there had been "significant failures of leadership".
Ms Leadsom's intervention is one of the most significant yet, as she campaigned for Vote Leave and endorsed Mr Johnson in the 2019 leadership contest.
She wrote: “The conclusion I have drawn from the Sue Gray report is that there have been unacceptable failings of leadership that cannot be tolerated and are the responsibility of the Prime Minister.
"Each of my Conservative MP colleagues and I must now decide individually on what is the right course of action that will restore confidence in our government.”
Ms Leadsom did not call for the PM to resign, but her public expression of discontent will alarm Downing Street.
Allies are desperately trying to shore up Mr Johnson’s leadership as celebrations to mark the Queen’s 70 years on the throne begin.
The PM is expected to attend a string of royal commemorations in the coming days as his fate increasingly hangs in the balance.
Supporters fear yet more Conservative MPs are set to submit letters demanding a confidence vote to Sir Graham Brady, chairman of the party’s 1922 Committee.
Once 54 are received, a secret ballot must be triggered.
Arts Minister Lord Stephen Parkinson, who was an adviser to Theresa May when she faced a confidence vote, insisted: "There's an awful lot of speculation about the numbers of letters that go in and past experience shows, not just then but before, the only person that knows how many letters that have been sent in is the chairman of the 1922 Committee.
"It's pretty pointless to speculate about the numbers before then, it's a distraction from the work of government and in government we're getting on with making sure that we grow the economy to help with the cost of living."
Former MP Justine Greening warned: “The reality is that all prime ministers ultimately either have to get a grip or get out and that is a political rule that even Boris Johnson will need to follow.”
Former Tory leader William Hague said Boris Johnson "is in real trouble here" and warned MPs "are moving towards having a ballot".
He told Times Radio: "Well I think Boris Johnson is in real trouble here and when an MP as reputable, as experienced, as respected as (Sir) Bob Neill who we were just listening to gives that opinion, that he's just given, that's very serious trouble for the Prime Minister and I think the Sue Gray report has been one of those sort of slow-fuse explosions in politics."
He said people had misread the situation and the PM was not out of the woods.
"It's still going along, a lot of people misread it really, the events of last week as meaning the trouble is over, Boris is free and that's actually not the mood in the Conservative Party which is very, very troubled about the contents of that report," he said.
"So I think the Conservative Party will need to resolve this one way or another, obviously because to be an effective party they either need to rally behind the Prime Minister they've got, or they need to decide to force him out and I think they're moving towards either next week or around the end of June, they are moving towards having a ballot, it looks like that."
