Dominic Cummings has accused Boris Johnson of falling “far below the standards of competence and integrity the country deserves" in a blog post where he denied leaking stories about government and claimed the prime minister wished to halt one inquiry to protect his fiancée’s friends.
After No.10 sources claimed last week that Cummings was responsible for a series of leaks, including text messages between Johnson and businessman James Dyson, Cummings addressed accusations against him in a 1,000 word blog post.
The former senior adviser and Vote Leave campaigner alleged that Johnson had deliberately sought to block an inquiry into another leak - the disclosure of details about the second lockdown - because the man accused, adviser Henry Newman, was his fiance Carrie Symonds's best friend.
A No.10 spokesperson said yesterday: "The PM has never interfered in a government leak inquiry."
Cummings, who dramatically left the government last November, said during the investigation, known in the media as the "chatty rat" story, he was informed by the cabinet secretary Simon Case that evidence led to "Henry Newman and others in that office".
He claims that the prime minister was upset about this, claiming he would have to fire Newman and this would cause "serious problems with Carrie as they're best friends".
Cummings then claimed Johnson said "perhaps we could get the cabinet secretary to stop the leak inquiry?". In response, the ex-spad claims he said it was unethical.
Other officials are aware that this happened, Cummings claimed. He also said the prime minister knows he is not the source of the leak.
On the revelation of the Dyson messages, in which the businessman texted Johnson to lobby him for reassurance over tax arrangments relating to the manufacturing of ventilators, Cummings said did not have those WhatsApp records.
He said: "I have not found the ones that were leaked to [BBC political editor] Laura Kuenssberg on my phone nor am I aware of being sent them last year."
Jack Doyle, the prime minister's new director of communications, was named in the blog post for making allegedly false accusations to the media about him.
A No.10 source quoted in The Times said: “Dominic is engaged in systematic leaking. We are disappointed about that. We are concerned about messages from private WhatsApp groups which had very limited circulation.
“The prime minister is saddened about what Dom is doing. It’s undermining the government and the party. It might be that Dominic feels bitter about what’s happened since he left – but it’s a great shame. Dyson was trying to do something for the good of the country.”
Cummings also denied a separate leak relating to the rocketing refurbishment costs of the prime minister's Downing Street flat, and that he hoped to get party donors to pay for it.
He said his opinion at the time was that doing so would be foolish and "possibly illegal".
An urgent parliamentary inquiry should now get underway, he said, to look at the government's conduct during the Covid crisis and take evidence from people under oath. He said he would cooperate and No.10 could publish every email he send during his time in Downing Street, between July 2019 and November 2020, as long as they did not impact on national security.
In a final stinging rebuke, he said: "It is sad to see the PM and his office fall so far below the standards of competence and integrity the country deserves."
In response to the Cummings blog, the No.10 spokesperson said: “This government is entirely focused on fighting coronavirus, delivering vaccines and building back better.”
The Downing Street flat refurbishment is rumoured to have involved interior designer Lulu Lytle and cost far more than the £30,000 annual public grant for the upkeep for the listed building. The government said today that it is considering whether the Downing Street estate works could be funded by a trust in the future, and that the PM had met the cost of this year's overspend personally.
Commenting on Cummings' remark that the proposed flat refurb arrangements could be unethical, a No.10 spokesperson said: “At all times, the government and ministers have acted in accordance with the appropriate codes of conduct and electoral law. Cabinet Office officials have been engaged and informed throughout and official advice has been followed.
“All reportable donations are transparently declared and published – either by the Electoral Commission or the House of Commons registrar, in line with the requirements set out in electoral law.
“Gifts and benefits received in a ministerial capacity are, and will continue to be, declared in transparency returns.”
Kate Proctor is the political editor of CSW's sister titles PoliticsHome and The House magazine, where a version of these stories first appeared.