A bid to hold a vote of no confidence in Boris Johnson and his government has been blocked.
Labour had sought to stage the vote in the House of Commons on Wednesday.
However, ministers rejected a motion put forward by the party, arguing that it would not be “a valuable use” of parliamentary time.
A No 10 spokesperson also accused Labour of “playing politics” by tabling the motion, with the Prime Minister already having announced his resignation.
Labour said that it was “unprecedented” for ministers not to allow parliamentary time for such a vote.
Criticising the Government, Labour added that the block represented a “flagrant abuse of power to protect a discredited prime minister”, while calling on Conservative leadership candidates to denounce it.
There have been calls for Johnson to step down after it was announced that he intends to carry on as Prime Minister until a new Conservative leader is installed in September.
Keir Starmer described it as “intolerable for the country” if Johnson is allowed to stay in No 10 until then.
“The Tory party has at last concluded that the Prime Minister is unfit for office – that was blindingly obvious a very, very long time ago,” said the Labour leader.
“They can’t now let him cling on for weeks and weeks and weeks, until September 5. It would be intolerable for the country.”
In practice, Labour’s motion had looked unlikely to succeed given that it could potentially trigger a general election.
That would require Conservative MPs to vote for it – or at least abstain in sufficient numbers – at a time when the party is effectively leaderless and trailing in the polls.
Labour, however, wanted to put on record where leadership contenders and their colleagues in the Commons stood on Johnson staying in office over the next two months.
Meanwhile, it was confirmed that eight candidates will be on the ballot paper when Conservative MPs begin to vote on Wednesday on who they want to succeed Johnson in office.
Rishi Sunak, Liz Truss, Tom Tugendhat, Kemi Badenoch, Penny Mordaunt, Jeremy Hunt, Nadhim Zahawi and Suella Braverman all secured the 20 nominations from fellow MPs needed to enter the contest.
Moments before the announcement, former health secretary Sajid Javid said he was pulling out of the race having apparently failed to attract enough support.
Earlier, transport secretary Grant Shapps announced that he was abandoning his bid and would be supporting Sunak, the former chancellor.
Backbencher Rehman Chishti – seen as the rank outsider – also said that he was dropping out having failed to get enough nominations.