Another five police officers are alleged to have placed bets on the timing of the general election.
The Metropolitan Police said it had been passed information on the allegations from the Gambling Commission.
It came after Rishi Sunak finally bowed to pressure and withdrew the Conservative Party’s support for two candidates embroiled in the betting scandal.
The Tories have dropped Craig Williams and Laura Saunders, both of whom are linked to the prime minister’s inner circle and are under investigation by the commission.
But two weeks after allegations first emerged even a Conservative former cabinet minister asked “why did it take so long”.
The commission is looking into alleged bets on the date of the election, made before Mr Sunak announced it would take place on 4 July.
Mr Sunak had withstood days of mounting calls to suspend those caught up in the row, with Northern Ireland minister Steve Baker the latest senior Tory to call for action.
In a bid to head off criticism on Monday, the prime minister announced the Conservatives were conducting their own probe into the row.
But a day later this party said “as a result of ongoing internal enquiries” it can no longer support either candidate.
Mr Williams, one of Mr Sunak’s closest aides as his parliamentary private secretary, appeared to admit placing a bet on the election date just days before the Tory leader announced it, saying he made a “huge error of judgement”.
Meanwhile, Ms Saunders, who is running in Bristol North West and has worked for the party since 2015, is married to Tony Lee, the Conservative Party’s director of campaigns, who is also being probed by the gambling watchdog.
Despite being ditched by their party both Mr Williams – who is standing in Montgomeryshire and Glyndwr – and Ms Saunders will still be on ballot papers, as the deadline to change these has passed.
Mr Baker piled pressure on Mr Sunak on Monday when he told ITV: “I would call them up and ask them, ‘Did you do it?’ And if they did it, then they are suspended.
“But the prime minister would have to answer why he hasn’t done it, I haven’t got inside information on why the prime minister hasn’t done it.”
He joined senior Tories including Tobias Ellwood who also called for them to be suspended.
After the announcement, a Conservative former cabinet minister, Lord Frost, tweeted: “We get there in the end. But why did it take so long to come to a decision that seemed so necessary right from the start?”
Others tied to the Gambling Commission probe include the party’s chief data officer Nick Mason, who has taken a leave of absence from Tory HQ.
A close protection officer for the prime minister has also been suspended by the Metropolitan Police and is being investigated.
Responding to the suspensions, Sir Keir Starmer told reporters: “Why didn’t that happen a week ago?”
And shadow paymaster general Jonathan Ashworth said: “It is yet another example of Rishi Sunak’s staggeringly weak leadership that it has taken him nearly two weeks to see what was obvious to everyone else.
