LONDON — Britain’s ruling Conservative party has become embroiled in a scandal concerning allegations that senior officials used inside knowledge to win bets on the date of the general election.

Five people connected to U.K. Prime Minister Rishi Sunak are being investigated for allegedly placing bets on the date of the July 4 election before it was announced by Sunak on May 22.

Nick Mason, chief data officer for the Conservative Party, is the latest Tory official to be probed by the Gambling Commission, according to a report in The Sunday Times. Mason has taken a leave of absence and his spokesperson denied any wrongdoing, the British newspaper reported. CNBC was unable to immediately confirm this and the Conservative Party has not yet responded to a request for comment.

Conservative MP for Montgomeryshire Craig Williams, who is also a close aide to the prime minister, was the first to face questions regarding a bet on the election date. He confirmed in a statement on X that he 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 through how it looks,” Williams added.

The Conservative Party’s campaign director Tony Lee, and his wife, Laura Saunders — the party’s candidate in Bristol North West — are also being looked into by the Gambling Commission.

Lee has taken a leave of absence, The Independent reported, and lawyers acting on behalf of Saunders told the newspaper that she will cooperate with the Gambling Commission and has nothing further to add. Saunders and Lee have not yet responded to a CNBC request for comment.

Lastly, one of Sunak’s police protection officers was arrested on June 17 on suspicion of misconduct in the public office after Britain’s Metropolitan Police was contacted by the Gambling Commission about alleged bets made by a police officer on the July polling day.

The officer was removed from operational duties and the matter has been referred to the Met’s Directorate of Professional Standard and the Independent Office for Police Conduct, London’s police force said in a statement.

The scandal comes amid sliding support for the Conservative Party, with one recent poll suggesting Sunak could be the first prime minister to lose his seat in a general election. Calls are growing for Sunak to suspend the party figures who are being investigated by the Gambling Commission.

“It’s very telling that Rishi Sunak has not already done that,” Keir Starmer, leader of the opposition Labour Party and favorite to win the upcoming general election, told reporters last week. “If it was one of my candidates, they’d be gone and their feet would not have touched the floor.”

Sunak declined to comment on whether those involved in the scandal should be suspended. Speaking during a televised BBC election event last week, Sunak said he was “incredibly angry.”

“What I can tell you is if anyone is found to have broken the rules, not only should they face the full consequences of the law, I will make sure that they are booted out of the Conservative Party,” Sunak told a live audience. Sunak told reporters on Monday that he and his family had not placed a bet on the timing of the election.

Michael Gove, secretary of state for leveling up, housing and communities and an outgoing Conservative lawmaker, told the Sunday Times that the betting scandal is as damaging for the Tories as the “partygate” scandal during the Covid-19 pandemic.

“If people have used inside information to place bets, that is deeply wrong,” Gove said on BBC News, adding that the act was “reprehensible.”

“I am deeply concerned by this ongoing speculation which is casting a shadow over the election. The public will be rightly appalled that anyone close the decision to call the election would use inside information to bet on an outcome they knew in advance,” McFadden wrote in his letter to the commission.