Sajid Javid has resigned as chancellor as Boris Johnson carries out a post-Brexit cabinet reshuffle.
Mr Javid rejected an order to fire his team of aides, saying “no self-respecting minister” could accept such a condition.
He had been due to deliver his first Budget in four weeks’ time.
The former home secretary was appointed chancellor by Mr Johnson when he became prime minister in July.
His resignation follows rumours of tensions between Mr Javid and the prime minister’s senior adviser Dominic Cummings.
Latest as Javid quits amid reshuffle
“He has turned down the job of chancellor of the Exchequer,” a source close to Mr Javid said.
“The prime minister said he had to fire all his special advisers and replace them with Number 10 special advisers to make it one team.
“The chancellor said no self-respecting minister would accept those terms.”
Chief Secretary to the Treasury Rishi Sunak is being tipped to replace Mr Javid – and there will be a new joint team of No 10 and 11 special advisers.
Mr Javid had been expected to remain in place, as the prime minister rejigs his top team.
In other reshuffle moves:
Northern Ireland Secretary Julian Smith and Business Secretary Andrea Leadsom have been sacked
Housing Minister Esther McVey and Environment Secretary Theresa Villiers are also out of the government
Attorney General Geoffrey Cox, who attended cabinet, was asked to resign by the PM