Rishi Sunak aide placed bet on election date days before announcement

Just three days later, Sunak announced that a general election would be held on July 4 in a surprise announcement.

In a statement, Williams said: “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 cooperate with these.

“I don’t want it to be a distraction from the campaign, I should have thought how it looks.”

A Conservative party spokesperson added: “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.”

The Guardian revealed that a red flag was automatically raised by Ladbrokes, as Williams was marked as a "politically exposed person".

The bookmaker is said to be particularly cautious over "novelty" markets.

The £100 bet could have led to a £500 payout on odds of 5/1.

It is thought to have been placed through an online account.

While the election announcement was a surprise to many MPs, the Prime Minister is thought to have been discussing the timing for months.

A spokesperson for the Gambling Commission said: “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.

“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.”