UK Prime Minister Boris Johnson is facing questions about the refurbishment of his flat on London's Downing Street amid allegations from his former advisor.
Dominic Cummings said in a blog post on Friday that Johnson had "plans to have donors secretly pay for the renovation (of his flat)" calling that "unethical, foolish, [and] possibly illegal".
Cummings said the refurbishment plans "almost certainly broke the rules on proper disclosure of political donations if conducted in the way he intended".
The charge is the latest in a string of allegations that Johnson and other Conservatives, including former Prime Minister David Cameron, blurred or broke rules relating to contacts with donors and business.
Opposition parties have picked up on the allegations ahead of local elections next month.
The UK government said that Johnson paid for the apartment refurbishment but the opposition Labour Party said the prime minister needed to explain how he obtained the money.
"It is about integrity. It is about taxpayers’ money. Every day there is more evidence of this sleaze. Frankly, it stinks," Labour leader Keir Starmer told the BBC on Saturday.
"Sunlight is the best disinfectant."
In his blog post, Cummings made other allegations including that the PM had tried to stop an inquiry into a leak of information about the second coronavirus lockdown because he heard it had involved his fiancée's friend.
"I told him that he could not possibly cancel an inquiry about a leak that affected millions of people, just because it might implicate his girlfriend’s friends," Cummings wrote in his post.
In a statement, Johnson’s Downing Street office said the prime minister had “never interfered” in the inquiry and that the government had “acted in accordance with the appropriate codes of conduct and electoral law” on issues involving the funding of the flat refurbishment.
Cummings, a former top advisor for Johnson, resigned in November.
He had become a controversial figure after driving 400 kilometres across the country during lockdown.
Cummings said he will answer questions about any of the issues he has raised when he appears before lawmakers on May 26.
The UK government is facing growing sleaze allegations largely linked to Cameron, who was prime minister between 2010 and 2016. A series of inquiries have been launched over Cameron's lobbying role for Greensill Capital, a financial firm which collapsed last month.