Boris Johnson has insisted he will not leave No 10 despite a mounting revolt against his leadership.
Ministers and aides have continued to submit their resignations, while support is ebbing away from the Prime Minister among previously-loyal MPs. However, Mr Johnson is understood to have told allies that he is "not going anywhere" and his critics should "calm down".
The resignations from a number of MPs and politicians followed a string of departures from the Government on Tuesday evening, led by Rishi Sunak and Sajid Javid, who delivered broadsides at Mr Johnson as they quit their Cabinet posts. Former health secretary Mr Javid is expected to add to Mr Johnson's problems with a personal statement in the Commons on Wednesday.
Rishi Sunak had been one of the Prime Minister’s strongest supporters – so what sparked this change of heart? Here’s what you need to know.
Why did Rishi Sunak resign?
The Prime Minister was battling to remain in No 10 as his handling of the row over scandal-hit former deputy chief whip Chris Pincher became the latest issue to raise questions over his judgment. A humiliating apology from the Prime Minister was unable to prevent the departure of two senior ministers and potential leadership rivals, with both writing incendiary resignation letters.
Mr Sunak said "the public rightly expect government to be conducted properly, competently and seriously", adding: "I believe these standards are worth fighting for and that is why I am resigning."
Nadhim Zahawi was then promoted to be the new Chancellor, with universities minister Michelle Donelan taking his place as Education Secretary.
Rishi Sunak resignation letter in full
Dear Prime Minister,
It is with deep sadness that I am writing to you to resign from the Government.
It has been an enormous privilege to serve our country as Chancellor of the Exchequer and I will always be proud of how during the pandemic we protected people's jobs and businesses through actions such as furlough.
To leave ministerial office is a serious matter at any time. For me to step down as Chancellor while the world is suffering the economic consequences of the pandemic, the war in Ukraine and other serious challenges is a decision that I have not taken lightly.
However, the public rightly expect government to be conducted properly, competently and seriously. I recognise this may be my last ministerial job, but I believe these standards are worth fighting for and that is why I am resigning.
I have been loyal to you. I backed you to become Leader of our Party and encouraged others to do so. I have served as your Chancellor with gratitude that you entrusted me with stewardship of the nation's economy and finances.
Above all, I have respected the powerful mandate given to you by the British people in 2019 and how under your leadership we broke the Brexit deadlock.
That is why I have always tried to compromise in order to deliver the things you want to achieve. On those occasions where I disagreed with you privately, I have supported you publicly.
That is the nature of the collective government upon which our system relies and it is particularly important that the Prime Minister and Chancellor remain united in hard times such as those we are experiencing today.
Our country is facing immense challenges. We both want a low-tax, high-growth economy, and world class public services, but this can only be responsibly delivered if we are prepared to work hard, make sacrifices and take difficult decisions.
I firmly believe the public are ready to hear that truth. Our people know that if something is too good to be true then it's not true. They need to know that whilst there is a path to a better future, it is not an easy one.
In preparation for our proposed joint speech on the economy next week, it has become clear to me that our approaches are fundamentally too different.
I am sad to be leaving Government but I have reluctantly come to the conclusion that we cannot continue like this.
Boris Johnson's reply to Rishi Sunak’s resignation
I was sorry to receive your letter resigning from the Government.
You have provided outstanding service to the country through the most challenging period for our economy in peacetime history.
In March 2020, weeks after your appointment as Chancellor, we introduced a national lockdown to protect people from the pandemic. You acted to safeguard the economy with the pace, creativity and commitment which has been the hallmark of your tenure.
The furlough scheme - conceived and implemented in a matter of weeks -supported 11.7 million jobs from 1.3 million employers. Through business loans and grants, you helped thousands of businesses to avoid insolvency. Emergency funding worth more than £140 billion, enabled the NHS and other critical public services to meet the enormous challenges we faced.
These efforts primed the economy for a rapid recovery once the immediate dangers of the pandemic receded. At the Spending Review last year, you put us on track to deliver our promises to the British people, including 20,000 police officers and 40 new hospitals. We also set a clear plan to rebuild our economy and public services, including an historic funding settlement for the NHS and delivering six million tutoring courses to help pupils catch up lost learning.
Through all of this, you have not shied from the tough decisions needed to repair our public finances whilst protecting public services and boosting economic growth. This has enabled us to provide support to households worth £37 billion, as we have faced global inflation pressures arising from Putin's brutal invasion of Ukraine.
And we have begun to deliver tax cuts to families - including this week, a cut to National Insurance saving the average worker £330 a year.
I have enormously valued your advice and deep commitment to public service and will miss working with you in government.
Additional reporting by PA.