One of Rishi Sunak’s closest parliamentary aides is facing a Gambling Commission probe after he “put a flutter” on when the General Election would take place.

Craig Williams, who served as the Prime Minister’s parliamentary private secretary and is the Conservative candidate for Montgomeryshire and Glyndwr, admitted to placing a bet on when the poll would take place “some weeks ago”.

The Conservative former MP, who represented Montgomery until the election was called, wrote on social media site X, formerly Twitter: “I’ve been contacted by a journalist about Gambling Commission inquiries into one of my accounts and thought it best to be totally transparent.

“I put a flutter on the General Election some weeks ago. This has resulted in some routine inquiries and I confirm I will fully co-operate with these. I don’t want it to be a distraction from the campaign. I should have thought through how it looks.”

The Guardian reported Mr Williams placed a £100 bet on a July election just days before Mr Sunak named the date as July 4, at a Ladbrokes in his constituency.

As a parliamentary aide, Mr Williams acted as a go-between for the Prime Minister and his MPs, and is understood to be a trusted member of Mr Sunak’s team.

The Guardian said the bet would have led to a payout of £500 based on 5/1 odds.

A Conservative Party spokesperson said: “We are aware of contact between a Conservative candidate and the Gambling Commission. It is a personal matter for the individual in question.

“As the Gambling Commission is an independent body, it wouldn’t be proper to comment further, until any process is concluded.”

A Gambling Commission spokesman said: “The Gambling Commission does not typically confirm or deny whether any investigations are under way unless or until they are concluded, or if arrests are made or charges are brought during a criminal investigation.

“If someone uses confidential information in order to gain an unfair advantage when betting, this may constitute an offence of cheating under Section 42 of the Gambling Act, which is a criminal offence.“

Labour’s Jonathan Ashworth, the shadow paymaster general, described what had happened as “utterly extraordinary”.

He said: “Rishi Sunak has sat on this information for more than a week but has lacked any backbone to take action. Once again, Rishi Sunak has been exposed as utterly weak.

“After all the Tory financial scandals, this is more evidence that the Tories have learned nothing, haven’t changed, and if given five more years, the chaos will just continue.

“Britain has the chance to turn the page on this failed Tory government which will heap £4,800 onto people’s mortgages. It’s time to rebuild with Labour.”