The controversy over the refurbishment of U.K. Prime Minister Boris Johnson's flat in Downing Street, and childcare spending were given fresh fuel when the country's Electoral Commission announced there were "reasonable grounds" to suspect an offense may have occurred.

Johnson has been pressed to justify how he paid for the apartment renovations, which have been estimated to have cost about £200,000 ($280,000) by British news outlets. Prime Ministers are given £30,000 ($41,000) in public funds each year to renovate the property while they are in office.

The British leader has since insisted on his innocence, telling the House of Commons that he "paid for Downing Street refurbishment personally."

The U.K. watchdog launched an inquiry into the Conservative Party's compliance with political donation laws on Wednesday, citing "fair grounds to believe that an offense or offenses might have occurred."

The problem is also being investigated by the government's top civil servant, Simon Case, and the prime minister's newly appointed adviser on ministers' interests, Lord Geidt.

Former aide Dominic Cummings accused Johnson of wanting donors to "secretly pay" for renovations to his residence in a "possibly illegal" move, and questions have been raised since.

Reports have also suggested Johnson borrowed money from the Conservative Party, which he is now repaying.

Foreign Secretary Dominic Raab refused to say who originally paid for the work and claimed he had "no idea" whether a donor was asked to cover Johnson's childcare costs.

"The last issue you asked about is an example of tittle tattle," Raab told Sky TV. He said Johnson had been "crystal clear" about the expenditure on the refurbishment of the apartment.

The Prime Minister and his government are currently facing multiple allegations of unethical conduct, a verbal spat with Cummings, and a potentially devastating charge that Johnson was willing to let people die to prevent a second pandemic lockdown in England.

The issues come ahead of local elections in England on Thursday, as well as elections for the Scottish and Welsh parliaments.