Nadhim Zahawi, who was appointed Chancellor on Tuesday evening, has told Prime Minister Boris Johnson to “do the right thing and go now”.
In a tweet accompanying a letter, Mr Zahawi said: “Prime Minister: this is not sustainable and it will only get worse: for you, for the Conservative Party and most importantly of all the country. You must do the right thing and go now.”
The letter from Zahawi reads: “I made clear to the Prime Minister alongside my colleagues in No 10 that there was only one direction where he was going and he should leave with dignity.”
A source close to Nadhim Zahawi told the PA news agency: “The country needs a Chancellor and he will serve as long as he’s asked to do so.”
The message from Zahawi comes as Education Secretary Michelle Donelan announced her resignation.
Donelan was only appointed on Tuesday evening to replace Nadim Zahawi after he was made chancellor.
In her resignation letter to the prime minister, she says "yesterday, I pleaded with you to do the right thing and resign for the sake of our country and our Party, both are more important than any one person".
"I see no way that you continue in post, but without a formal mechanism to remove you it seems that the only way this is only possible, is for those of us who remain in Cabinet to force your hand".
She says the PM has put ministers in an "impossible situation".