Dominic Cummings has said his campaign to oust Boris Johnson is "unpleasant but necessary... like fixing the drains" in his latest attack on his former boss.
The ex-No10 aide branded the Prime Minister a "complete ****wit" and accused Mr Johnson and his wife Carrie of "rattling around in there and ****ing everything up for everyone".
In an interview with New York Magazine, Mr Cummings accused the PM of being obsessed with infrastructure projects that can act as "monuments to him" like a Roman emperor.
And he claimed Mr Johnson was fixated on media coverage of matters such as whether Big Ben would bong for Brexit rather than policy issues.
Downing Street declined to comment on his latest tirade against the PM.
The former Vote Leave campaigner has gone to war with his former boss after being forced out of Downing Street in November 2020 following a power struggle.
Mr Cummings, who famously faced a public backlash for his lockdown trip to Durham, stoked the partygate saga engulfing No10 by revealing the bash on May 20 2020 - a BYOB drinks party in the Downing Street garden.
He admitted he was trying to oust the PM, which he said was “an unpleasant but necessary job.
"It’s like sort of fixing the drains," he added.
Mr Johnson was critical in delivering Brexit and defeating Jeremy Corbyn at the 2019 election, the ex-aide said.
“But after that what’s the point of him and Carrie just rattling around in there and ****ing everything up for everyone and not doing the job properly,” he said.
Mr Cummings said he got fed up in January 2020 by the Prime Minister's obsession with whether Big Ben would toll on Brexit day.
"I was sitting in No. 10 with Boris and the complete ****wit is just babbling on about: ‘Will Big Ben bong for Brexit on the 31st of January?’
"He goes on and on about this day after day. Eventually I say to him: ‘Who cares? What are you talking about?
"Why are you babbling on about Big Ben? It’s completely ludicrous. We won the election a few weeks ago. We have an eighty-seat majority."
He claimed the PM, who supposedly dreamed of being world king as a child, is fixated on "what would a Roman emperor do".
Mr Cummings said the PM fantasises about “monuments to him in an Augustine fashion. ‘I will provide the money. I will be a river to my people. I will provide the money that builds the train station in Birmingham.’ Or whatever. ‘And it will have statues to me, and people will remember me after I am dead like they did the Roman emperors.’"
His latest intervention comes as the Prime Minister battles to save his premiership from the fallout of the Downing Street party saga.
Top civil servant Sue Gray is expected to hand over her highly anticipated report into allegations of lockdown-flouting parties as early as tomorrow.
But her inquiry was thrown into chaos after the Metropolitan Police demanded key details on parties it is investigating be stripped out.
Today, Foreign Secretary Liz Truss said Mr Johnson is "absolutely" the best person to lead the Tories into the next general election.
Asked if she is tempted by the top job, she told the BBC's Sunday Morning programme: "There is no contest. There is no discussion."
