Prime Minister Rishi Sunak said Thursday he was "incredibly angry" after more Conservative Party figures were put under investigation over alleged bets placed on the UK general election date.

Facing questions on the growing scandal from an audience of voters on live television, the beleaguered leader said any election candidates or officials found to have broken rules would be kicked out of the party.

His comments came hours after the Conservatives' campaign director stepped aside following reports that he and his wife, a Tory candidate in the July 4 election, were under investigation by betting regulators.

Last week, another would-be MP, Craig Williams, who was a Sunak ministerial aide, was also being probed for staking £100 (US$127) on the date before it was called.

London police said on Wednesday that one of the prime minister's police security detail had been arrested for allegedly placing a bet on the date.

"I was incredibly angry... to learn of these allegations," Sunak said of the cases involving his party officials.

"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," he added.

The Conservatives confirmed earlier that campaign director Tony Lee had started "a leave of absence" and that the Gambling Commission was looking into "a number of individuals".

The regulator did not name individuals but the BBC reported that Lee and his election candidate wife Laura Saunders were under investigation. Her lawyers said she would "be co-operating with the Gambling Commission" and claimed the report infringed her privacy rights.

The commission had already said it was looking at the claims regarding Williams.

Political bets are allowed in the UK, including on the date of elections, but using insider knowledge to do so is against the law. (AFP)