Theresa May is "a dead woman walking" who will have to be replaced as Prime Minister, former Chancellor George Osborne has declared.
As May reeled from losing her Commons majority after the general election, the Evening Standard editor twisted the knife, warning that the Tories now had to dump a "hard Brexit" to survive.
Speaking on BBC1's Andrew Marr Show, Osborne was withering about the woman who had sacked him from the Cabinet last year and suggested she could be challenged for the Tory leadership early as next week.
"Theresa May is a dead woman walking - it's just how long she can remain on death row," he said.
"I think we will know very shortly – in other words we could easily get to the middle of next week and it all collapses for her.
"Or if it doesn't, and I agree that a lot of Tory MPs don't want a leadership campaign now, it will be delayed."
He added "but be in no doubt" there would be a change. "You've got the Prime Minister who's supposed to have won the election in hiding."
And in a further blow to May's authority, Defence Secretary Michael Fallon revealed that he had told the PM that she had to now open up her style of government beyond a narrow circle of advisors.
"I and other colleagues have made that clear to her. A minority government will require a collective approach," he said, adding that the Tory backbench 1922 Committee and all Tory MPs had to be consulted on the way forward.
Former Education Secretary Nicky Morgan also said on ITV's Peston on Sunday that there was no way May could be allowed to stay on.
"It's fairly clear that Theresa May cannot lead us into another general election. If we are going to have another leadership election in the Conservative party, what we cannot do is have another 'coronation'."
Osborne said May"can't just blame the advisers" who urged her to go for a snap election and who oversaw a "disastrous" manifesto.
May's former co-chiefs of staff, Nick Timothy and Fiona Hill, both quit after heavy criticism that they were responsible.
Some allies of the PM have blamed campaigns guru Sir Lynton Crosby and even Brexit Secretary David Davis for the blunders, but Osborne said May was the one in charge.
"You see what's left of 'the May-ites' blaming Lynton Crosby. I worked with Lynton Crosby during the 2015 election, a very successful campaign, with Lynton Crosby and Mark Textor [his pollster] they are professionals," he said.
"The idea that they are responsible for Mrs May's failure to communicate or the disaster of the manifesto strikes me as trying to blame other people for your own mistakes.
"In the end the only person who decides to have a General Election is the Prime Minster. The only person who decides what's in the manifesto, is the Prime Minister".
Osborne also ripped into May for failing, in her Downing Street statement after the election, to apologise to those Tory MPs who lost their seats to Jeremy Corbyn's "surge".
"The thing that made the Tory party cross is when Theresa May returned to Downing Street and never mentioned the many good MPs who had lost their seats, like Nicola Blackwood or Kris Hopkins or Simon Kirby," he said.
"The Tory party, and I was watching it, was absolutely furious that there was no acknowledgement of the loss and suffering that had been caused."
And he laid into the way May had taken the Tories 'backwards' on the gains made by himself and David Cameron.
"I'm someone who spent years getting the Conservative Party back into office, winning in seats like Bath, like in Brighton, like in Oxford West," he said.
"And I am angry like many Conservatives are that we have gone backwards, that we are undoing the good work of the last 10 years. And I'm not afraid to say that."
Osborne also pointedly revealed what May had said to him when she fired him last year after she became Prime Minister: "She said I needed to get to know my party better."
Relishing the PM's discomfort, the ex-Chancellor even pointed to a Gerald Scarfe cartoon in the Sunday Times which showed Corbyn as a dog "relieving himself on Theresa May", saying it was a fine caricature in the tradition of British cartoons.
Crucially, Osborne said that a deal with Ulster's Democratic Unionist Party (DUP) would force May to abandon a hard Brexit because it wanted to maintain economic ties with Ireland.
Osborne said: "That claim she can do 'no deal' is blown apart".
He attacked the "permanent leadership campaign" of Boris Johnson, but said Tory MPs wanted a new leader.
Osborne, who appeared on the show before Jeremy Corbyn, was also snapped by journalist Toby Young laughing and chatting with the Labour leader.
Defence Secretary Michael Fallon hit back at Osborne: "George is enjoying his job as a commentator rather than a player on the pitch".
But former Tory minister Anna Soubry warned on SkyNews: "We need to put that sense of the economy and the nation's interest at the forefront. None of this messing about behind the scenes.
"She's got to open up, be more consensual in the way she operates, to listen to people like Philip Hammond and Greg Clark, who represent business so well in the Cabinet.
"If she does those things she can lay down the way for her to leave and then we will have a new Prime Minister."
Lord Heseltine, who was sacked by May from his job as an adviser to ministers, also told the Marr Show that a hard Brexit was the biggest issue.
"Brexit is the cancer gnawing at the heart of the Conservative party. There's a lot of talk of changing leader, it may well come to that. But it's not about just changing the leader, it's about changing the policy."