Boris Johnson covered the renovation costs for his Downing Street flat “from his own pocket”, Trade Secretary Liz Truss told the BBC.
She said that work had been “fully declared”, but she did not answer repeated questions on whether a Tory party donor initially provided the money to him.
It comes after the PM’s former chief adviser, Dominic Cummings, claimed Johnson had a “possibly illegal” plan for donors to pay the refurbishment.
Labour said questions remained, as details over how the work was paid for had yet to be made public.
The government is supposed to publish the list of minister’s interests twice a year, but the last one showing money donated to them was released in July 2020.
Speaking on the BBC’s Andrew Marr Show, Labour deputy leader Angela Rayner said Mr Johnson should come in front of MPs on Monday to answer questions and publish the list “as the public deserves [to see] it”.
Johnson lives in the flat above 11 Downing Street with his fiancee Carrie Symonds – a move echoing a number of his predecessors as it is bigger than the accommodation above No 10.
In March, Downing Street dismissed as “speculation” suggestions that refurbishments on the flat last year would be paid for by Tory donors through a charity set up for this purpose, amid reports that the costs had spiralled out of control.
But on Friday, Cummings launched a blistering attack on his former boss via his blog, claiming he advised the PM 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”.
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.”
And Cabinet Office Minister Lord True told the House of Lords on Friday that “any costs of wider refurbishment in this year have been met by the prime minister personally”.
Donations and loans to political parties of more than £7,500 must be reported to the Electoral Commission, which said it was having “discussions with the Conservative Party”, but had not yet launched an investigation.
The controversy also comes amid an ongoing row over lobbying in Westminster, after revelations former prime minister David Cameron had texted ministers about the financial firm he was working for and businessman Sir James Dyson had directly contacted Mr Johnson over tax issues when working on ventilators during the pandemic.