At least seven Metropolitan Police officers are being investigated over bets on the timing of the General Election.

The Met and the Gambling Commission issued an update on the inquiry into the alleged use of inside information to bet on the July 4 date.

Scotland Yard had previously indicated that six officers were under investigation, including one of Prime Minister Rishi Sunak’s protection team who was arrested on suspicion of misconduct in public office.

So far five Conservatives have also been caught up in the inquiry, with reports suggesting the figure could be 15 parliamentary candidates and officials, although the gambling watchdog has not confirmed the numbers involved.

The Gambling Commission is focused on allegations of cheating, which are likely to make up the majority of cases, while Scotland Yard will lead on what is likely to be a much smaller number of cases where there could be additional offences such as misconduct in public office.

Gambling Commission chief executive Andrew Rhodes said: “We are focused on an investigation into confidential information being used to gain an unfair advantage when betting on the date of the General Election.

“Our enforcement team has made rapid progress so far and will continue to work closely with the Metropolitan Police to draw this case to a just conclusion.

“We understand the desire for information; however, to protect the integrity of the investigation and to ensure a fair and just outcome, we are unable to comment further at this time, including the name of any person who may be under suspicion.”

Detective Superintendent Katherine Goodwin, who is leading the Met investigation, said: “We have agreed a joint approach with the Gambling Commission, who are the appropriate authority to investigate the majority of these allegations.

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

On Tuesday, Mr Sunak caved in to mounting calls to withdraw support for two parliamentary candidates facing an investigation by the gambling regulator – his parliamentary aide, Craig Williams, and Laura Saunders.

Ms Saunders’ husband, Tony Lee, the Conservative Party’s director of campaigning, has taken a leave of absence, as has Tory chief data officer Nick Mason, while Senedd member Russell George stepped back from the shadow cabinet in the Welsh Parliament after being placed under investigation.

Labour has also been dragged into the row, suspending candidate Kevin Craig after he was investigated by the regulator for betting on himself to lose the contest in Central Suffolk and North Ipswich.

Sir Philip Davies, the husband of Cabinet Office minister Esther McVey, became the latest Tory candidate to be accused of gambling on the election.

He reportedly bet £8,000 against himself holding his marginal Shipley constituency, according to The Sun.