Boris Johnson is expected to make ministerial appointments shortly as he seeks to continue in office until a new Tory leader is elected.
“The prime minister will shortly make new appointments to his ministerial team,” a No 10 source said.
It comes as Mr Johnson prepares to announce his resignation, quitting as Tory leader in a statement to the nation on Wednesday.
He aims to remain in office until his successor is elected by the Conservative Party – a process that could conclude in September.
But some Conservative MPs have already raised doubts over whether the prime minister, who has haemorrhaged support in the last 48 hours, will able to fill ministerial posts in a “caretaker” government.
The interim is normally uncontroversial, but never before has a prime minister initially refused to leave power after a cabinet revolt, or previously broken other laws and conventions.
George Freeman, who quit as science minister today, tweeted: “Boris Johnson needs to hand in the seals of office, apologise to Her Majesty & advise her to call for a Caretaker Prime Minister To take over today”.
It would allow ministers to “get back to work & we can choose a new Conservative Leader to try & repair the damage & rebuild trust”, he added.
Keir Starmer, the Labour leader, also said Mr Johnson should go immediately, adding: “None of this nonsense about clinging on for a few months. Enough is enough”.
Speaking in the Commons, however, Cabinet Office minister Michael Ellis said the government will continue to function, telling MPs “other secretaries of state can deal with the issues for other departments, constitutionally and legally in necessary circumstances”.
“I cannot pre-empt the Prime Minister’s statement,” he said. “And the House and the nation will hear more very shortly, but Government and the civil service will continue to function in the meantime.
“The business of the House statement will be made shortly, and members can ask questions of the Leader of the House of Commons about the matter of the business of this place.
“But the House will continue to function, and Government business will continue to function.
“Other secretaries of state can deal with the issues for other departments, constitutionally and legally in necessary circumstances.”