Dominic Cummings has left Downing Street after internal battles over his role as Boris Johnson’s chief adviser, according to the BBC.
The BBC understands he will continue to work from home, on issues such as mass coronavirus testing, until the middle of December.
The prime minister is said to want to “clear the air and move on”.
Mr Cummings has been at the heart of a No 10 power struggle, which has also seen communications director Lee Cain leave.
Several Tory MPs have welcomed the pair’s departure as a chance for Mr Johnson to make a fresh start.
The BBC’s Political Editor Laura Kuenssberg said Mr Cummings departure from No 10 had been brought forward given the “upset in the team” in Downing Street, for which she said it had been a “difficult week”.
She said there had been long-running tensions between different factions in No 10 but this “slow burning fuse exploded fast when it finally happened”.
Dominic Cummings and Lee Cain are long-time colleagues, having worked together on the Leave campaign during the EU referendum.
When Mr Cain’s exit was announced on Wednesday, it prompted rumours that his ally would also step down.
In response, Mr Cummings told the BBC “rumours of me threatening to resign are invented” but said his “position hasn’t changed” since he wrote in January that he wanted to make himself “largely redundant” by the end of 2020.
Boris Johnson worked with Mr Cummings on the 2016 Vote Leave campaign and hired Mr Cummings to be his senior adviser, when he became prime minister.
Six months later the pair’s “Get Brexit Done” campaign message helped Mr Johnson win a large majority in the general election.
Mr Cummings became more of a public figure in the past year and was forced into holding his own news conference at Downing Street in the summer, following controversy over him making a trip to the north of England when non-essential travel was banned at the height of the coronavirus lockdown.
He had a notoriously difficult relationship with Conservative MPs, several of whom have welcomed his exit and said it was time for things to be done differently in Downing Street.
“Both Dominic Cummings and Lee Cain were pretty dismissive of backbenchers and sometimes ministers and secretaries of state, and I don’t think that was helpful,” said former Northern Ireland secretary Theresa Villiers.
“I do think it’s important that whoever takes over has a different approach.”
Sir Bernard Jenkin said it was time to restore “respect, integrity and trust” between No 10 and Tory MPs while veteran Conservative MP Sir Roger Gale said it was “an opportunity to muck out the stables”.