The British Conservative Party have withdrawn support from two candidates – Craig Williams and Laura Saunders – after they were implicated in an investigation into gambling ahead of the UK general election next week.

Party leader Rishi Sunak acted after coming under mounting pressure within the party to take a tougher stance on the alleged use of inside information to bet on the timing of the 4 July poll.

Mr Williams, who was the Prime Minister’s parliamentary aide, and Ms Saunders who is standing in Bristol North West, will no longer have the support of the party.

Because nominations have closed, Mr Williams – who is standing in Montgomeryshire and Glyndwr – and Ms Saunders will both still be on the ballot paper.

However a Conservative Party spokesman said: “As a result of ongoing internal inquiries, we have concluded that we can no longer support Craig Williams or Laura Saunders as parliamentary candidates at the forthcoming General Election.

“We have checked with the Gambling Commission that this decision does not compromise the investigation that they are conducting, which is rightly independent and ongoing.”

Labour leader Keir Starmer said: “Why didn’t that happen a week ago?”

As well as the candidates, two senior Tory officials have taken a leave of absence at a crucial point in the election campaign, after being drawn into the Gambling Commission investigation.

Ms Saunders’ husband Tony Lee, the party’s director of campaigning, and chief data officer Nick Mason, have stepped back from their duties.

And a police officer who served in Mr Sunak’s protection team has been arrested on suspicion of misconduct in public office over alleged bets on the election date.

Mr Sunak has been under pressure to act amid Tory concerns the issue was further damaging their electoral chances.

Steve Baker became the first serving minister to call for those who placed bets on the election date to be suspended by the party last night.

The Minister of State for Northern Ireland told ITV’s Peston programme that Mr Sunak should take action: “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.”

Meanwhile the Metropolitan Police said it was “simply untrue” to say that the force had leaked the names of people suspected of using inside information to bet on the election date.

A source close to the Cabinet Office told the Daily Telegraph the Gambling Commission is telling the Met “and then almost instantly these names are finding their way to journalists”.

“The suspicion very much is, it’s the Met,” the source said.

The newspaper reported that a further five police officers are currently under investigation by the gambling regulator.

A Met spokesman said: “The allegations that the Met has leaked information are simply untrue. We continue to liaise with the Gambling Commission and are assessing information they have provided.”