Boris Johnson is being urged to explain how the refurbishment of his Downing Street flat was paid for, following allegations from his ex-chief advisor.
Dominic Cummings claimed the PM had once had “possibly illegal” plans to get Tory donors to fund the work.
The government said “costs of wider refurbishment in this year have been met by the prime minister personally.”
But Labour said he needed to fully disclose who paid for the work in the first place.
Party leader Sir Keir Starmer said: “Publish the details, have the full inquiry. If there’s nothing to see here… have a full inquiry.”
“Every day there’s more evidence of this sleaze and frankly it stinks,” he added.
It comes amid a row over the lobbying of ministers, including the prime minister, after it was revealed he had exchanged text messages with businessman Sir James Dyson.
Once Mr Johnson’s closest ally, Mr Cummings was forced out of his Downing Street role at the end of last year, following an internal power struggle.
In a blistering attack on his old boss on Friday, Mr Cummings questioned the prime minister’s “competence and integrity”.
In his first blog post since leaving his role, Mr Cummings:
- denied leaking text messages sent between Mr Johnson and Sir James
- denied leaking details of the second coronavirus lockdown in England in November
- claimed the prime minister once had a “possibly illegal” plan for donors to pay for renovations of his Downing Street flat
- alleged Mr Johnson had considered trying to block an inquiry into the leak in case it involved a friend of his fiancee Carrie Symonds
No 10 said the PM had never interfered in a government leak inquiry.
Mr Cummings promised to answer questions about “any” issues when he appears before a Parliamentary inquiry into the government’s pandemic response on 26 May.
In his blog, Mr Cummings claimed the prime minister once planned to have donors “secretly pay” for renovation of his official Downing street flat.
Like several of his recent predecessors, Mr Johnson is living in the flat above No 11 Downing Street, which is larger than the one above No 10.
He added that Mr Johnson “stopped speaking to me about the matter in 2020”, as he told him the renovation plans were “unethical, foolish, possibly illegal and almost certainly broke the rules on proper disclosure of political donations if conducted in the way he intended”.
Mr Cummings said he would be “happy to tell the cabinet secretary [Simon Case] or Electoral Commission” what he knew about the matter but that his knowledge is “limited”.
The Electoral Commission says it is working to establish whether any of the spending on the flat needs to be examined within its own remit on political donations, and therefore needs to be reported and subsequently published.
‘Cronyistic cabal’
In response to Mr Cummings’s claims, 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.”
Former attorney general Dominic Grieve said the issue was “just one illustration of the chaos Mr Johnson seems to bring in his wake”, describing the prime minister as “a vacuum of integrity”.
The former Conservative MP, who was expelled from the parliamentary party by Mr Johnson in 2019 after rebelling against him in a Brexit vote, also described his government as “a cronyistic cabal”.
Lockdown leak
Mr Cummings also denied being the source of a leak ahead of the second coronavirus lockdown in November, which saw details of the plans for new restrictions appear in several newspapers.
In his blog, he said an inquiry at the time found that neither he nor the then-Downing Street director of communications, Lee Cain, had been responsible.
He added that the events around that inquiry “contributed to [his] decision to stick to [his] plan to leave No 10 by 18 December”, which he said were “communicated to the prime minister in July”.
Mr Cummings also claimed Mr Johnson had considered stopping the inquiry.
He wrote that he recalled a meeting between Mr Johnson and the cabinet secretary at the time, after an inquiry had been launched, at which the cabinet secretary allegedly said “all the evidence definitely leads to Henry Newman and others in that office”.
At the time, Mr Newman was a special adviser at the Cabinet Office. He took up a role in Downing Street earlier this year.
Mr Cummings claimed that, in a conversation he had with the PM afterwards, Boris Johnson said: “If Newman is confirmed as the leaker then I will have to fire him, and this will cause me very serious problems with Carrie [Symonds – the PM’s fiancee] as they’re best friends… [pause] perhaps we could get the cabinet secretary to stop the leak inquiry?”
In response to Mr Cummings’ claims, a Downing Street statement said: “The prime minister has never interfered in a government leak inquiry.”
And a senior government official said: “The allegations against Henry Newman are entirely false. He wouldn’t be working in Downing Street if he was suspected of leaking information.”
Dyson row
Mr Cummings also denied leaking text messages between the prime minister and Sir James Dyson, following newspaper reports suggesting this.
He said he was “happy to meet with the cabinet secretary and for him to search my phone for Dyson messages” and “for No 10 to publish every email I received and sent July 2019-November 2020”.
Mr Cummings called for an “urgent Parliamentary inquiry into the government’s conduct over the Covid crisis”, adding that he thought Mr Johnson had fallen “far below” the standards of “competence” the “country deserves”.
Sir Alistair Graham, former chairman of the Committee on Standards in Public Life, said if Mr Cummings could give evidence about the prime minister’s alleged incompetence this could be “very damaging”.
The text exchange between the prime minister and the businessman occurred in March last year, after the government asked companies to help build thousands of ventilators needed for the pandemic response.
In it, the prime minister agreed to “fix” concerns the businessman had about tax bills for his Singapore-based staff if they moved to the UK to do this.