Boris Johnson and the Conservatives are facing calls to be investigated over potential law breaking after it was reported the party paid the initial costs for refurbishing his Downing Street flat.
ITV’s political editor Robert Peston has reported the party paid the Cabinet Office for the refurbishment, but that the prime minister is now repaying the party.
Any payment by the party, or one of its donors, would have to be – or should have been – declared as a loan under party funding rules.
Responding to the report on Monday evening, one senior MP called for a public inquiry amid the "dodgy donor" row.
Watch: Ministers quizzed over Boris Johnson's Downing Street flat refurbishment
It comes after three ministers refused to say who made the initial payment for the renovations, which reportedly ran as high as £200,000.
Liz Truss, Ben Wallace and Michael Gove would only say Johnson has covered the costs, without being drawn on the initial payment.
Speaking earlier on Monday, Johnson himself did not deny discussing using donors to fund the work, saying: “If there’s anything to be said about that, any declaration to be made, that will, of course, be made in due course.”
Ian Blackford, the SNP’s Westminster leader, said in response to the ITV report: "The Tory sleaze scandal continues to grow. More revelations and serious questions about Boris Johnson’s dodgy donor scheme.
"There must be an independent public inquiry into allegations of special access, impropriety and possible illegality."
Labour deputy leader Angela Rayner said: “If the PM or the Conservative Party accepted a donation to do up the PM's flat and failed to declare this donation then they broke the law. It's that simple.
"It doesn't matter that the PM subsequently paid it back. So where did the money come from PM?"
Johnson has been embroiled in the scandal since Dominic Cummings, his former chief adviser, claimed the PM wanted donors to “secretly pay” for the flat refurbishment in a move which Cummings said would have been “unethical, foolish, possibly illegal”.
Last week, the Daily Mail published details of an email from Tory peer Lord Brownlow in which he said he was making a £58,000 donation to the party “to cover the payments the party has already made on behalf of the soon-to-be-formed ‘Downing Street Trust’”. To date, no such trust has been formed.
The Electoral Commission, which first raised the issue with the Conservatives more than a month ago, confirmed at the weekend it was still looking into whether any of the sums relating to the work on the flat should have been declared.
Labour attacked the government over the row in the House of Commons on Monday, with shadow chancellor of the Duchy of Lancaster Rachel Reeves saying Johnson "is now corrupting the standards of public life expected in high office".
Dame Angela Eagle also asked: “Dominic Cummings has described the PM's plans to get Tory donors to pay for the lavish refurbishment of the Downing Street flat – and I’m quoting – ‘unethical, foolish and illegal’.
"So either the PM's former chief adviser is a liar and fantasist or the PM is not being entirely straightforward with the House or the country, which is it?”
Michael Gove, for the government, said "all donations to the PM or any other MP, or indeed political parties, will be declared appropriately and properly".
According to the Ministerial Code, a list of ministers' interests is meant to be published twice a year. However, none have been published since July last year.
Watch: Government Lobbying Scandal Explained