Dominic Cummings leaves Downing Street on Friday evening carrying a box
Mr Cummings told the BBC that “rumours of me threatening to resign are invented” after speculation that he would follow communications director Lee Cain in leaving Number 10.
Downing Street 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.
On Friday evening, Mr Cummings was seen leaving Downing Street carrying a box.
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.”
Earlier, 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.
Dominic Cummings arriving at Downing Street on Friday
It comes just a day after a bitter power struggle in Number 10 led to the resignation of Mr Cain.
He had been offered the post of chief of staff but a backlash among Tories and Mr Johnson’s inner circle ultimately led him on Wednesday to announce his departure from Number 10 rather than a promotion.
Mr Cummings and Mr Cain are close political allies, having worked together since the Brexit campaign. Mr Cummings was said to be unhappy with the way his friend had been treated.
The Telegraph reported an “associate” of Mr Cain as saying the communication chief’s departure was the “beginning of the end for Dom”.
“Lee is the person who has been covering Dom’s flank 24 hours a day and he will soon be gone,” the source told the paper.
Conservative MPs have urged Mr Johnson to use events to reshape the team inside Downing Street and reconnect with the parliamentary party, some of whom feel he has been “lost” to advisers over the past year.
Sir Charles Walker, vice chairman of the 1922 Committee, told BBC Newsnight: “If Boris, the Prime Minister, gets the chief of staff position right – he gets the right person in that position – he will plant his standard firmly back in the middle of the Conservative parliamentary party.
“We feel we’ve lost him for the last year. We want him back – he belongs to us, he doesn’t belong to the advisers, he belongs to the parliamentary party that elected him and he got elected at the last general election.”
But any MPs hoping for a softer approach in the government's position to a future trade deal with Europe, would have been left disappointment on Friday after Downing Street vehemently denied Mr Cummings’ exit would soften the UK’s negotiating stance in post-Brexit trade negotiations with Brussels.
The Prime Minister’s official spokesman said: “Absolutely not. That is simply false. The Government’s position in relation to the future trade agreement negotiations is unchanged.”
The infighting spilling into the open sparked criticism from Tory MPs.
Conservative backbencher Sir Roger Gale told the PA news agency: “The Government, and Downing Street particularly, should be concentrating all of its efforts on the pandemic and on the end game of Brexit, and frankly this is a distraction that cannot and should not be allowed to take place and the Prime Minister has got to get a grip on it.”
But Transport Secretary Grant Shapps told ITV News Mr Cummings' "ideas and energy" will be missed.
"Dominic Cummings is someone who would shake up the consensus, and sometimes you do need someone in the room who’s saying, ‘but why? Why are we doing it like that? Have we thought of this other approach’," he said.
"It’s good and healthy to have someone around who does that."
Mr Shapps added that Mr Cummings had also planned to leave at the end of year, once Brexit and the transition period were over. "I'm not surprised that it feels like a lot of his ideas are done."
Meanwhile, Senior Conservative MP Theresa Villiers said Dominic Cummings’ departure from No 10 will be “a good opportunity for a fresh start”.
The Prime Minister’s official spokesman James Slack, who confirmed he would be replacing Mr Cain when he departs in the new year, insisted that Mr Johnson was not being distracted from the national crisis by the bitter row.
“You’ve seen from the Prime Minister this week that he’s absolutely focused on taking all the steps that are required to equip the country to beat coronavirus,” the spokesman said on Thursday.
Mr Slack, a former Daily Mail journalist who also served as Theresa May’s official spokesman when she led the country, said he would remain a civil servant when he succeeds Mr Cain.
In his resignation statement, Mr Cain confirmed he had been offered a promotion to the key position of the Prime Minister’s chief of staff.
The move – which would have meant he was one of just a handful of people in No 10 with direct one-to-one access to Mr Johnson – was seen as entrenching the grip of the Vote Leave faction on the Downing Street operation.
However it ran into immediate resistance, with Mr Johnson’s fiancee, Carrie Symonds – who has clashed in the past with Mr Cummings – reportedly strongly opposed to the appointment.
Ms Symonds is a former Tory press chief who has served as a special adviser in previous governments.
Allegra Stratton, the former ITV and BBC journalist brought in to host televised Downing Street news conferences from next year, was also said to have objected to the appointment.
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