Prime Minister Theresa May’s two closest advisers have quit after the Conservatives failed to win a majority of MPs in the general election.
The BBC understands the PM was warned she faced a leadership challenge unless she sacked Nick Timothy and Fiona Hill.
Labour said the pair had “taken the fall” for the prime minister.
Mrs May has announced that the new Downing Street chief of staff is ex-Conservative MP and former housing minister Gavin Barwell.
Mr Timothy said he took responsibility for his role in the “disappointing” result and the widely-criticised manifesto package on social care.
The BBC’s assistant political editor Norman Smith said the pair’s departure bought the PM some “breathing space” following 24 hours of recriminations after the Conservatives lost their overall majority.
He said the two were so close to the PM that critical MPs believed that, unless they made way, she would not be able to change her leadership style to adopt a more “outgoing, inclusive, responsive, empathetic approach”.
Mrs May has said she intends to stay as prime minister and on Saturday evening it was announced her party’s chief whip had agreed an outline deal “in principle” with the DUP of Northern Ireland, which would see the unionist party support the Tories on key votes.
Mr Timothy and Ms Hill both stepped down amid mounting pressure on Mrs May to overhaul the way No 10 worked and broaden her circle of advisers.
Announcing his resignation on the Conservative Home website, Mr Timothy urged Tory MPs to “get behind” Mrs May but said nothing should be allowed to get in the way of the process of forming a government and beginning Brexit talks.
He said the Conservatives’ failure to win was not due to a lack of support for Theresa May and the Conservatives but due to an “unexpected surge” of support for Labour.
Who were the PM’s special advisers?
Fiona Hill: Fiercely loyal and seen as a formidable operator, Fiona Hill was at Mrs May’s side for four years at the Home Office, becoming a close confidante of the then home secretary. A former Sky News and Scotsman journalist in her 40s, she led work on the Modern Slavery Act and published her own report on the subject.
She was forced to resign as Mrs May’s special adviser in a 2014 dispute with Michael Gove over who was to blame for briefing newspapers about an increase in extremism in schools. But she was brought back into the fold when Mrs May became PM.
Nick Timothy: The bearded Brummie is the son of a steelworker, who went to grammar school and joined the Conservative Party at the age of 17. He is credited with influencing the PM’s views on social mobility and the need to put the Conservatives “at the service of working people”.
His ambition to be a Conservative MP was reportedly thwarted by David Cameron, following a row over special advisers being asked to canvass in a by-election.
He conceded his party had failed to communicate a sufficiently “positive” message to voters and address their concerns over years of austerity and inter-generational divisions, including over Brexit.
“We were not talking to the people who decided to vote for Labour,” he said.
He defended the party’s “honest and strong” manifesto, saying controversial proposals to use the value of peoples’ homes to fund domiciliary care costs had been discussed in government for months and were not his own personal “pet project”.
But he added he took “responsibility for my part in this election campaign, which was the oversight of our policy programme” and “I regret the decision not to include in the manifesto a ceiling as well as a floor in our proposal to help meet the increasing cost of social care”.
Ms Hill said it had been a pleasure to serve in government and she believed Mrs May would continue as prime minister.
Norman Smith said he understood that senior Conservatives had warned the PM they would instigate a leadership contest at a meeting of backbenchers early next week if the pair did not leave, and were confident they could get the required 48 signatures to trigger a contest.
One former minister, Anna Soubry, welcomed the clearout, saying it was the “right thing to do” and saying the PM must “build a consensus” on Brexit and other issues.
But Labour’s deputy leader Tom Watson said the PM’s advisers had “taken the fall” for her but tweeted the PM was “responsible for her own defeat”.