Fresh claims emerged of a “toxic” workplace culture after a source claimed Carrie Symonds and incoming press secretary Allegra Stratton had been characterised as “manipulative scheming b*****” by rivals inside Number 10.
An ex-Cabinet minister today said Mr Cummings’ relationship with the Prime Minister “fell off a cliff”.
The now highly-publicised power struggle inside Number 10 was first laid bare on Wednesday, after news leaked that Mr Cain had been offered the job of Mr Johnson’s chief-of-staff.
Hours later, Mr Cain had announced his resignation. His promotion had been opposed by Miss Symonds and Ms Stratton, the former ITV journalist who is set to become the face of government White House-style briefings in January.
The pair are said to have been the subjects of hostile counter briefings as warring factions inside Number 10 grappled for power.
A source told the Standard: “They were coming for Carrie and Allegra as manipulative scheming b****** when they were only being clear-eyed about the kind of morals and conduct they wanted at the heart of power.
“There were briefings against them with lies.
“Boris has done so well but they bullied and bossed him about. To watch it in meetings was unpleasant.
“They thought they were the Prime Minister. But they were so far from that. They were dragging Boris down.”
Whitehall sources have compared how Mr Cain was treated to the case of Sajid Javid’s former special adviser Sonia Khan.
Ms Khan was sacked and escorted out of Downing Street by police on the orders of Mr Cummings, who claimed she was leaking information.
Some media reports have said Mr Cummings has quit his post with immediate effect.
According to the PA News agency, he and Mr Cain will still be employed until the middle of next month, with other reports suggesting Mr Cummings will work from home on projects such as mass testing.
A source said: “It’s one rule for the senior boys, another for the female aides.”
Senior Tory MPs have now called on Mr Johnson to use Mr Cummings’ departure to “reset the Government” following complaints the party and Parliament had been sidelined.
Former Brexit secretary David Davis told BBC Breakfast many within Number 10 had “turned on” Mr Cummings.
He said: “It is said… people ranging from Allegra [Stratton] – the new spokesman for the Prime Minister – right through to his [Mr Johnson’s] fiancee, Carrie, turned against him.
“The relationship with the Prime Minister fell off a cliff. And once that’s gone, it’s gone.”
Mr Davis, who was allegedly described as “thick as mince” and “lazy as a toad” by Mr Cummings when in the Cabinet in 2017, also branded the adviser’s style “confrontational”.
But he added that the PM had “relied on him” and “there are things he (Mr Cummings) was right about”.
He added the photos of Mr Cummings leaving Downing Street could help “reset Government”.
He told BBC Breakfast: “The photograph will last the weekend and people will remember it, but it’s not the key.
“And at one level, as I said, Boris will want to reset Government and in a sense, that photograph does part of the resetting for him.”
Theresa May’s ex-chief of staff Lord Gavin Barwell told BBC Radio 4’s Today programme: “It feels to me that there’s an opportunity here for [Boris Johnson] to get his Downing Street operation more harmonious and more effective.
“And, perhaps, to set a less confrontational and more unifying tone, that is maybe more in tune with his natural instincts.”
It comes after the Daily Telegraph reported that Mr Cummings had told colleagues Mr Johnson was “indecisive”, and that he Mr Cain relied on Cabinet Office minister Michael Gove for clarity.
According to the Daily Mail, tensions were raised further when the Prime Minister was shown “hostile texts” briefing against Miss Symonds, which had been forwarded to her.
Mr Cummings left his north London home on Saturday afternoon but only spoke to reporters to ask them to move out of his way, and did not answer any questions.
He was seen getting into a Toyota Prius which drove away from the scene.
Earlier, his wife Mary Wakefield came outside and told reporters he “would not come out” in the rainy weather.
Sir Edward Lister was announced as the interim chief of staff pending a permanent appointment.
The dramatic events have come as Brexit heads to a crucial phase next week, as London seeks a trade deal with Brussels before the end of the transition period on December 31.
The Prime Minister’s official spokesman, James Slack, who will replace Mr Cain in the new year, insisted Mr Johnson was not being distracted by the row.
“What the Prime Minister and the Government are focused upon is taking every possible step to get this country through the coronavirus pandemic,” he said.