The Metropolitan Police said that it was investigating a “small number” of wagers which could include some that were placed by politicians.

Det Supt Katherine Goodwin, who is leading the force’s investigation, said the Gambling Commission would pursue “the majority” of allegations.

She added: “There will, however, be a small number of cases where a broader criminal investigation by the police is required.”

So far five senior Conservatives have been publicly named as being under investigation by the Gambling Commission in relation to election bets.

Mr Williams was interviewed by investigators from the watchdog on Wednesday after reporting placing a £100 bet on the timing of the snap poll.

Laura Saunders has also been suspended as a Tory candidate in Bristol after it emerged that she is being looked at by the Commission.

She is married to Tony Lee, the Conservative Party’s director of campaigning, who is also being investigated as is Nick Mason, its head of data.