Downing Street has refused to deny reports that Boris Johnson is considering setting up a charity to pay for the refurbishment of his official flat.
The Daily Mail reported that the scheme – based on one used by the White House – could be funded by wealthy Tory benefactors.
The move comes amid reported concerns over the spiralling costs of the refurbishment of the flat over No 11 overseen by Mr Johnson’s fiancee, Carrie Symonds.
However, it raised questions over possible conflicts of interest, offering a potential backdoor way of providing a financial benefit to the Prime Minister.
Mr Johnson’s press secretary Allegra Stratton described the report as “speculation”, while his official spokesman referred journalists to the Cabinet Office annual report and accounts – which have yet to be published for the relevant period.
“That is where we set out the details of what has happened,” the spokesman said.
“Downing Street is a working building as has been the case under successive administrations, refurbishment and maintenance are made periodically.”
Ms Stratton added: “Downing Street is maintained to appropriate standards for the Grade I and II listed building that it is.
“The Cabinet Office sits in oversight of that. As things stand there is already a process in place for maintaining it to the right standard.”
According to the Mail, Mr Johnson is reported to have complained the cost of refurbishment – which is now said to be complete – was “totally out of control” and had run to “over a hundred grand”.
The paper said he had told one minister that he was particularly concerned about the cost of the wallpaper chosen by Ms Symonds, saying she appeared to have ordered “gold wall coverings”.
Labour MP Sarah Owen called on Mr Johnson to disclose how much taxpayers’ money had been spent on the refurbishment project.
In a letter to the Prime Minister, she challenged him to say whether he considered it appropriate to accept payments direct from Tory donors.
“This latest case raises more issues in relation to this Government’s mishandling of public money,” she said.
“Can you foresee any potential conflicts of interests with you personally taking direct payments from Conservative Party donors?”
Earlier, Mr Johnson denied that members of his No 10 team were at war with each other, following a series of hostile press briefings aimed at Ms Symonds.
In an interview with The Sun, the Prime Minister insisted his Downing Street operation was a “nest of singing birds” and that they were “mono-maniacally” focused on dealing with the Covid pandemic.
It follows the dramatic departure last year of Mr Johnson’s chief adviser Dominic Cummings after he reportedly clashed with Ms Symonds in a bitter No 10 power struggle.