Craig Williams, Rishi Sunak’s private secretary, was also placed under investigation over a £100 “flutter”, which he apologised for and described as a “huge error of judgment.”

Meanwhile, one of Mr Sunak’s close protection officers has also been arrested on suspicion of misconduct in public following a similar allegation and is suspended as an internal investigation is carried out by Scotland Yard.

Michael Gove, the outgoing Housing Secretary, compared the betting scandal to partygate during Boris Johnson’s premiership. Mr Gove told The Sunday Times: “It looks like one rule for them and one rule for us… That’s the most potentially damaging thing.

“The perception that we operate outside the rules that we set for others

“That was damaging at the time of partygate and is damaging here.

“If you’re in a privileged position [close] to the prime minister at the heart of a political operation and you use inside information to make additional money for yourself, that’s just not acceptable. So if these allegations are true, it’s very difficult to defend.”