Sir Oliver Dowden (Image: Getty)
Former deputy prime minister Sir Oliver Dowden has reportedly been interviewed in the investigation into betting on the date of the general election.
He becomes the most senior ally of to be questioned by the Gambling Commission, the statutory body that regulates betting in the UK.
He follows Mr Sunak’s former parliamentary aide Craig Williams and ex-Downing Street chief of staff Liam Booth-Smith.
It is understood Mr Sunak has not yet been interviewed in the probe.
The inquiry, which was launched in June, is set to continue for another three to six months.
The commission is investigating whether bets were placed on a July election by people with inside knowledge, which would be in breach of gambling rules, ahead of Mr Sunak’s shock announcement on May 22.
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 added: “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.”
A source close to Sir Oliver said he is not and was never under investigation himself.
It is understood Sir Oliver spoke to the police involved with the Gambling commission in early summer to assist with their inquiries as part of their investigation into others.