In terms of betting on the general election date, Sir Oliver Dowden has emerged as the most senior individual questioned by the Gambling Commission.

The authority that oversees betting in the UK has now questioned the former deputy prime minister, who was Rishi Sunak's buddy.

It was stated by Sky News that while "numberous people," including officials from the Conservative Party, had been interrogated, Mr. Sunak had not yet been.

Hundreds of documents have also been seized as part of the investigation.

A source close to Sir Oliver said the former senior cabinet minister is not and was never under investigation himself.

News of the developments comes on the first day of the Conservative Party conference in Birmingham.

Sir Oliver was knighted in Mr Sunak’s dissolution honours, announced less than an hour before the polls closed on 4 July.

The commission is investigating whether bets were placed that an election would be held in July by people with inside knowledge in the days leading up to the shock announcement of the election date on 22 May. This would be in breach of gambling laws.

‘Case will continue for three to six months’

A source told Sky News: “The general election betting investigation is still ongoing. Hundreds of documents have been seized by the Gambling Commission from CCHQ.

“The Gambling Commission has also employed more ex-police as investigators to take the case forward. It’s expected the case will continue for three to six months.”

Asked if Mr Sunak has been interviewed, the source said: “I don’t believe so. Numerous people have been interviewed, in and out of CCHQ.

“Gambling Commission investigators have made numerous visits to CCHQ. Oliver Dowden was interviewed.”

The scandal erupted in June when Craig Williams, formerly MP for Montgomeryshire and Mr Sunak’s parliamentary private secretary, admitted he was being investigated by the Gambling Commission.

Mr Williams had placed a £100 bet on a July election at Ladbrokes in his constituency just days before Mr Sunak announced on 22 May that the election would be held on 4 July. Based on odds at the time, he would have won £500.

The Conservative Party was approached for comment.