Rishi Sunak has resigned as chancellor, telling the Prime Minister that standards in Government are “worth fighting for”.

The chancellor resigned shortly after 6pm on Tuesday evening, shortly after health secretary Sajid Javid.

It leaves two major roles empty in Mr Johnson’s Cabinet and plunges the Prime Minister into one of the most serious crises of his leadership.

In the letter, published on Twitter, the now former chancellor said that he could no longer remain loyal to the Prime Minister, who remains mired in scandal over the appointment of Tory MP Chris Pincher to the role of deputy chief whip.

Mr Pincher quit as deputy chief whip last week following claims that he groped two men at a private members’ club, but Mr Johnson was told about allegations against him as far back as 2019.

The Prime Minister acknowledged he should have sacked Mr Pincher when he was told about the claims against him when he was a Foreign Office minister in 2019, but instead Mr Johnson went on to appoint him to other government roles.

Mr Sunak, tipped as potential future leader of the Conservative Party, told the 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.”

Mr Sunak said that he had always tried to “compromise” to support the Prime Minister in his aims.

“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,” he said.

But Mr Sunak said that he could no longer back Mr Johnson, as he said that the approaches of the two men were “fundamentally too different”.

He added: “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.”