As the latest ‘sleaze’ allegations about donors giving money to the PM took a foul turn, it was also reported that Mr Johnson told friends he needs to earn about £300,000 a year — twice his salary — to keep his head above water.

According to the Sunday Times, one donor said they were asked to pay the bill for a nanny for Wilfred, the 1-year-old child of Mr Johnson and his fiancé Carrie Symonds.

A former Number 10 insider also told the paper it was ‘received wisdom’ that the PM is permanently broke.

A prominent MP was allegedly handed a complaint from a Tory donor unhappy about being asked for money.

The unnamed donor said: ‘I don’t mind paying for leaflets but I resent being asked to pay to literally wipe the prime minister’s baby’s bottom’, reports claimed.

Downing Street insists that Mr Johnson has covered the cost, but did not say whether he footed the bill initially.

Similar questions have been raised about the renovation of his Downing Street flat – which Mr Johnson says he has paid for, but it is unclear if someone else was reimbursed for the initial cost.

The Electoral Commission this week launched an investigation into whether any donations or loans to pay for the lavish refurbishment of his Downing Street flat were properly declared.

He has also been under pressure over reported comments that he would rather see ‘bodies pile high’ than impose a third coronavirus lockdown, on top of a lobbying row and allegations of cronyism.

Labour’s Sir Keir Starmer has repeatedly labelled the allegations ‘sleaze’.

But on Sunday morning Foreign Secretary Dominic Raab branded the allegations ‘tittle tattle’ and said he had ‘no idea’ if a Tory donor was asked to pay childcare costs.

He told Sky’s Sophy Ridge on Sunday: ‘I have no idea, you don’t have conversations like that with the PM. I can’t comment on every little bit of gossip that’s in the newspapers.

‘The last thing you asked me about, I think, is an example of tittle tattle.’

Asked if there was a second invoice for refurbishments of the Prime Minister’s Downing Street flat settled directly with a supplier, he said: ‘As the Prime Minister has set out this week, he covered the cost himself, he’s followed all the relevant codes of conduct at all relevant times, he took official advice all along the way.

‘There are three reviews now, I think, into this and I think the right thing for me to do is not add political commentary that could otherwise prejudice those reviews, but to respect the integrity of them, so I’m not going to offer you, I’m afraid, any more commentary, or if you like chatter, on the various different reports and speculation that I see in the Sunday papers.’

Mr Johnson’s salary puts him close to the top 1 per cent of UK earners but he does earn significantly less than many world leaders.