Boris Johnson remains as prime minister despite his two most recent cabinet appointments calling for him to resign.
Chancellor Nadhim Zahawi, who was given the job two days ago, said the situation was ânot sustainable and will only get worseâ.
And Education Secretary Michelle Donelan quit, saying Mr Johnson had âput us in an impossible situationâ.
But Mr Johnson insists he has a âcolossal mandate to keep goingâ.
The wave of resignations from the government and party exceeded 50 on Thursday, as Northern Ireland Secretary Brandon Lewis became the first cabinet member of the day to quit, quickly followed by seven other ministers.
Previously loyal supporters â Priti Patel and Grant Shapps â urged him to step down on Wednesday.
Meanwhile, Attorney General Suella Braverman has said she will stand in any leadership challenge, although she has not resigned.
In his resignation letter on Thursday, Mr Lewis said: âI have given you, and those around you, the benefit of the doubt.
âI have gone out and defended this government both publicly and privately. We are, however, now past the point of no return.â
Treasury minister Helen Whately, security minister Damian Hinds, science minister George Freeman, pensions minister Guy Opperman, technology minister Chris Philp, and courtsâ minister James Cartlidge also then resigned in swift succession.
Taking aim at his critics, the prime minister sacked Levelling Up Secretary Michael Gove in a shock move on Wednesday, with a Downing Street source describing Mr Gove as a âsnakeâ who âgleefully briefs the press that he has called for the leader to goâ.
Mr Gove, a former ally in the Brexit campaign who then derailed Mr Johnsonâs first bid for the Tory leadership, had urged the PM to resign earlier in the day.
Boris Johnson has a long history with Michael Gove â who he sacked after Mr Gove called for the PM to quit
More than 40 ministers and aides quit on Wednesday â a record for a 24-hour period.
Even late into the night, the resignations continued, with Welsh Secretary Mr Hart standing down just before 23:00 BST.
He had been among a group of cabinet members who attempted to persuade the prime minister to stand down, which also included Mr Johnsonâs former close allies Home Secretary Ms Patel, Transport Secretary Mr Shapps and Business Secretary Kwasi Kwarteng.
Later on Wednesday night, former loyalist Ms Braverman joined the calls for Mr Johnson to quit, telling ITVâs Peston he had handled matters âappallinglyâ in recent days.
She said she would not resign as it was her duty to carry on in her current job â but added: âIf there is a leadership contest, I will put my name into the ring.â
Former Health Secretary Matt Hancock also withdrew his backing for the PM, saying he had âsupported him through thick and thinâ but he now needed to go.
Mr Hancock â who said he would not be running for the leadership â predicted Mr Johnson would not be leader for much longer, âwhether thatâs tomorrow or next weekâ.
A standoff between the prime minister and swathes of the Conservative Party, from the cabinet down.
The last two days have robbed Boris Johnson of much of his authority; but not yet his job.
He is still there in Downing Street â determined and defiant, his government pockmarked by unfilled ministerial vacancies after a slew of resignations.
Mr Johnsonâs career has been defined by a convention smashing attitude.
That style now confronts what some fear could soon be a constitutional conundrum: what happens if the prime minister wonât budge.
The former Northern Ireland Secretary Julian Smith said it was a âdisgraceâ â âour system works on confidence, he has lost it,â Mr Smith said, fearing what he called a âmajor constitutional situationâ.
Conservative backbenchers who want rid of the prime minister still have another option â changing the rules, next week, so another vote of confidence in him could be held.
But some cabinet ministers â Deputy Prime Minister Dominic Raab, Culture Secretary Nadine Dorries, Brexit Opportunities Minister Jacob Rees-Mogg remain loyal to the prime minister.
And justifying Mr Johnson staying in the role, a No 10 source said: âThe prime minister has a mandate from 14 million people to get a job doneâĤ party wants to stop him they have to take that mandate away.â
The BBC has also been told Mr Johnson has been stressing that millions voted for him, and questioning whether any of his would-be successors would be able to âreplicate his electoral success at the next electionâ.
Mr Johnson appeared in front of the Liaison Committee earlier on Wednesday â a group of MPs which scrutinises government decisions and policies.
He ruled out calling a snap general election, saying the earliest date he can see for one is 2024.
The PM survived a confidence vote last month and under current rules he is immune from another challenge for 12 months.
But there are elections next week to the top team of the 1922 Committee, which organises the confidence votes. Rebel Tories want to get elected so that they can push through a rule change so that a confidence vote can be held sooner.
Suella Braverman has put her hat in the ring to be the next leader of the Conservative Party
The wave of resignations was triggered by revelations about the prime ministerâs handling of sexual misconduct allegations against former Deputy Chief Whip Chris Pincher.
On Tuesday, it emerged that Mr Johnson had been personally briefed about a complaint against Mr Pincher in 2019 when the Tamworth MP was a minister in the Foreign Office.
It contradicted days of denials from No 10 that the prime minister had known of any formal complaints about Mr Pincher, and prompted resignations that evening by two key cabinet colleagues, Chancellor Rishi Sunak and Health Secretary Sajid Javid.
Mr Javid told the Commons in his resignation speech on Wednesday that âenough was enoughâ and âthe problem starts at the top and I believe that is not going to changeâ.
The row is the latest issue to prompt Conservative MPs to question the prime ministerâs leadership and direction of government.
Mr Johnsonâs government has been dogged by a series of controversies in recent months, not least by a police investigation into parties in Downing Street during lockdown.
Some Tory MPs have also expressed dissent over tax rises, the governmentâs response to rising living costs and its policy direction.
BBC