Video report by ITV News Political Correspondent Daniel Hewitt
Boris Johnson’s senior adviser Dominic Cummings has left Number 10 with immediate effect, ITV News understands.
The prime minister's controversial aide had been expected to stand down at the end of the year, but he has quit his role immediately.
Mr Cummings was seen carrying boxes away from Downing Street on Friday evening before the reports emerged.
The aide had insisted that "rumours of me threatening to resign are invented", after it was suggested he would exit in protest over the treatment of his fellow Vote Leave veteran Lee Cain, who quit as Downing Street's director of communications on Wednesday.
Mr Cain's resignation came less than 24 hours after it was reported that he was to be promoted to the key position of the prime minister’s chief of staff.
Mr Cummings and Mr Cain will continue to work for the prime minister until mid-December but will not return to Downing Street, ITV News Political Editor Robert Peston understands.
Guto Harri, former adviser to Boris Johnson said Mr Cummings had to go.
He said: "Most of the public should have never heard of Dominic Cummings but they do because he imposed laws on the rest of us that he ignored himself. And went on then to treat us as idiots giving the most preposterous excuse for his behaviour and thinking we were mad enough to take it.
"You can't have someone at the heart of public life who treats the public with contempt."
Dominic Cummings leaving Number 10:
Gavin Barwell, former chief of staff to former Prime Minister Theresa May, tweeted: "Big moment: Boris now has an opportunity to get a more harmonious, effective Downing Street operation (like he had at City Hall); improve relations with the parliamentary party; and lead a less confrontational, more unifying government that better reflects his own character."
Tory backbenchers urged Number 10 to use the exit of the aide, whose mid-lockdown trip to Durham cemented his notoriety, as an opportunity to restore the values of “respect, integrity and trust”.
Senior Conservative MP Theresa Villiers said it will be “a good opportunity for a fresh start”.
The former environment secretary said: "Clearly there are concerns about the dismissive attitude sometimes shown by Lee Cain and Dominic Cummings towards people in Government and MPs on the backbenches."
She added: "I think introducing an atmosphere which is more collaborative, cooperative and actually one achieves more when one is positive and respectful about colleagues."
But Transport Secretary Grant Shapps said: "Dominic Cummings is somebody who would shake up the consensus and often you do need somebody in the room who's saying 'but why - why are we doing it like that? Have we thought of this other approach?'
"And actually it's good and healthy to have someone around who does that."
But former Tory home secretary Amber Rudd showed her apparent appreciation of Mr Cummings’ departure.
After her daughter, journalist Flora Gill, tweeted a picture of Mr Cummings exiting Number 10 with a box captioned “Gonna print this picture out and stick it at the top of my Christmas tree *chefs kiss*”, Ms Rudd wrote: “She is a very annoying daughter.
“But sometimes she is wise.”
Tory former deputy prime minister Lord Heseltine, president of the European Movement UK, said: “In an interview in March, I forecast Dominic Cummings would be gone by Christmas.
“I can think of no man who has done so much harm to this country in so short a time.
“He has left a generation to pay the price of Brexit.”
Watch ITV News Political Editor Robert Peston on Cummings' departure:
Senior Tory MP Sir Bernard Jenkin said: “It’s an opportunity to reset how the Government operates and to emphasise some values about what we want to project as a Conservative Party in Government,” the chair of the Commons liaison committee told BBC Radio 4’s Today programme.
“I’m not surprised in a way that it is ending in the way it is. No prime minister can afford a single adviser to become a running story, dominating his Government’s communications and crowding out the proper messages the Government wants to convey.
“Nobody is indispensable.”
Brexit Party leader Nigel Farage tweeted: “It is well documented that I have never liked Dominic Cummings but he has backed Brexit.
"Seeing him leave Number 10 carrying a cardboard box tells me a Brexit sell-out is close."
Liberal Democrat leader Ed Davey simply tweeted: “Not before time”.
Deputy Labour leader Angela Rayner tweeted: “I have no interest in Dominic Cummings’ apparent ‘legacy’. In the middle of a pandemic he shattered public trust and undermined lockdown & our fight against Covid. His cross-country road trip, long distance eye test, dishonesty & arrogance was an insult to the British people.”
Shadow health secretary Jonathan Ashworth highlighted the strain being heaped on the NHS and the public by Covid-19 while “Downing Street is paralysed by the soap opera of these self-indulgent spin doctors,” adding: “It’s pathetic.”
His colleague David Lammy, shadow justice secretary said: "Dominic Cummings has been one of the most malign influences on the British government in modern history.
“His legacy is one of bullying, deception, hypocrisy and hubris. The super-forecaster who ignored the pandemic. His damage is irreparable.”
SNP Westminster leader Ian Blackford said: “Boris Johnson’s most senior advisers are abandoning the Prime Minister like rats on a sinking ship – just as the UK faces a devastating extreme Brexit, a second wave of coronavirus, and a growing Tory unemployment crisis.
“It tells you everything you need to know about this arrogant, incompetent and self-serving Tory Government that they are ditching their responsibilities – at the exact moment their reckless decisions are causing the maximum damage to people across the UK.
“If the Prime Minister had a shred of integrity he would pack his own bags and go with them."
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A spokesman for Number 10 said: "The Prime Minister has today asked Sir Edward Lister to take on the role of chief of staff for an interim period pending a permanent appointment to the post."
On Thursday, Mr Cummings had said that his “position hasn’t changed since my January blog” when he wrote that he hoped to make himself “largely redundant” by the end of 2020.
Downing Street had declined to say whether Mr Cummings had formally handed in his notice, whether he had told Mr Johnson of his departure or whether an exit date had been set.
The Prime Minister’s official spokesman said: “I don’t have anything for you on that other than pointing back to Dom’s words which are being reported… I think they speak for themselves.”