If found guilty, the right-wing populist could be suspended from the House ⁠of Commons for a period of time.

Reform UK leader Nigel Farage is facing an investigation by the Parliamentary Commissioner for Standards over a $6.7m (5 million pound) gift from a party donor, days after the anti-immigrant party emerged as the biggest winner in local and regional elections.

A spokesperson for Reform UK denied any wrongdoing on Wednesday, telling the Reuters news agency that “[Farage] has ⁠always been clear that this was a personal, unconditional gift and no rules were broken.”

“We look forward to this being put to bed once and for all,” the spokesperson added.

Farage said he accepted the donation from Thailand-based billionaire and crypto investor Christopher Harborne to pay for his personal security before he announced his candidacy in the 2024 national election that brought ‌him into Parliament.

He said it was not a political donation, but rival political parties in April accused him of breaking rules, which require members of parliament to declare donations received in the year preceding an election within one month of taking office.

The party has topped every national opinion poll since early last year, prompting increased scrutiny of the party’s sources of funding. Last week, elections for about 5,000 seats on 136 local councils in England, as well as in the devolved parliaments in Scotland and Wales, marked significant progress for Reform UK, including in areas considered Labour heartlands.

If the investigation finds ⁠Farage committed a serious breach of parliamentary declaration rules, he could be suspended from the House ⁠of Commons for a period of time. A suspension of 10 days or more could trigger a recall petition, potentially forcing him to stand in a special election for his seat.

About ⁠two-thirds of Reform’s funding last year came from Harborne, according to Electoral Commission data. Opponents say the funding from an overseas billionaire demonstrates a gulf between the image Farage cultivates as a man of the people willing to take on the establishment and his dependence on wealthy donors.

Reform’s deputy leader, Richard Tice, said at the weekend that voters already knew about the gift and had still chosen to vote in large numbers for the party in last week’s elections.

Earlier this year, Farage apologised after he was found by the parliamentary authorities to have inadvertently committed 17 breaches of ‌rules ‌on declaring financial interests, including payments from Google and Elon Musk’s X Corp.

Parliament’s Standards Commissioner concluded the failures were unintentional and caused by staffing and other administrative issues.