Boris Johnson plans to stand down as prime minister if he wins a second term so he can "make money and have fun", according to his former chief aide.
Dominic Cummings also took aim at Mr Johnson's style of chairing crucial coronavirus meetings by alleging he shouts "forward to victory", does a thumbs-up and swiftly departs the room before anyone can disagree with him.
Downing Street declined to deny many of the allegations made in the blog post on Wednesday but did describe the claim Mr Johnson plans to stand down in around 2027 as "utter nonsense".
Mr Cummings, who left No 10 in November when an internal power struggle spilled out into public, alleged the problems within government will not be fixed by the public inquiry into the handling of the coronavirus pandemic.
"It will not start for years and it is designed to punt the tricky parts until after this PM has gone - unlike other PMs, this one has a clear plan to leave at the latest a couple of years after the next election, he wants to make money and have fun not 'go on and on'," he added.
"So we either live with chronic dysfunction for another (roughly) five years or some force intervenes."
The prime minister's press secretary refuted the allegation that Mr Johnson was planning on standing down.
"The PM has actually been asked this before and has said himself it's utter nonsense, so that still stands," she said.
"As you know, the PM was elected in 2019 and continues to focus on delivering the manifesto we were elected on and leading the county out of the pandemic."
Elsewhere in the 7,000-word-plus blog, Mr Cummings took aim at the prime minister's ability to chair crucial meetings on the COVID-19 crisis.
He praised Dominic Raab, who stood in for Mr Johnson when he was in hospital with coronavirus, saying the foreign secretary was far more effective because he can "chair meetings properly instead of telling rambling stories and jokes".
Mr Cummings said Mr Raab "let good officials actually question people so we started to get to the truth unlike the PM who as soon as things get 'a bit embarrassing' does the whole 'let's take it offline' shtick before shouting 'forward to victory', doing a thumbs-up and pegging it out of the room before anybody can disagree".
Asked if it was an accurate characterisation of Mr Johnson's style, the prime minister's press secretary said: "We're not going to engage with allegations made on these issues."
Mr Cummings also wrote that Mr Johnson twice described Health Secretary Matt Hancock as "hopeless" early in the coronavirus pandemic.
Mr Cummings published a series of screenshots purportedly showing WhatsApp exchanges between himself and the prime minister to combat what he said are "lies" from No 10.
The blog post exceeding 7,000 words is the latest salvo in a bitter row between the former aide, Mr Johnson and the Health Secretary, who Mr Cummings blames for many failings during the crisis.
Australian Associated Press