The Gambling Commission has widened its inquiry into bets on the date of the general election, it has been reported.

Sky News has said that investigators have written to leading bookmakers asking for details of bets of £20 or more placed only days before Rishi Sunak announced that there would be a July election.

The watchdog will also look at whether people with inside knowledge may have asked a third party to place a bet for them.

ITV reported that an initial trawl by the Commission had brought to light “many names” to investigate.

Mr Sunak announced the date of the election on 22 May, and it has since emerged that at least two MPs and two other senior Tory figures placed bets that the poll would be in July.

Nick Mason, the Conservative party’s chief data officer, was reported to have been told that he was part of the inquiry into betting on the date of the election before it was public knowledge.

The Conservative Party confirmed to The Sunday Telegraph that he had taken a leave of absence.

Tony Lee the party’s director of campaigning and his wife Laura Saunders, a candidate in Bristol North West are also under investigation. 

The loss of two senior figures at a time when Labour’s poll lead over the Tories remains stubbornly around 20 points gives Mr Sunak a further headache in the closing stages of the campaign.

James Cleverly, the Home Secretary, on Sunday said he had no reason to believe that ministers had placed bets on the election date. 

Michael Gove, the Levelling Up Secretary, compared the impact of the row with the Partygate scandal.

“It looks like one rule for them and one rule for us,” he told the Sunday Times, adding: “That’s the most potentially damaging thing.”

Mr Gove went on to suggest it was “just not acceptable” for those in a “privileged position” close to the Prime Minister to use what he described as “inside information to make additional money for yourself”.

He added: “You are, in effect, securing an advantage against other people who are betting entirely fairly and without that knowledge. So if these allegations are true, it’s very difficult to defend.”

The latest gambling allegations were published by The Sunday Times, which claimed dozens of bets had been placed with potential winnings worth thousands of pounds.

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