The Gambling Commission is still investigating potential breaches of the Gambling Act. Police also said an officer attached to the Royalty and Specialist Protection Command - arrested in June on suspicion of misconduct in public office - would have no further action taken against him over this particular offence.

Politicians and police officers were placed under investigation earlier this year after it was alleged they had used insider information to place bets on the date of the general election.

The Gambling Commission began investigating those suspected of cheating under Section 42 of the Gambling Act.

However, the Met police took charge of inquiries into a "small number of cases" where other offences, such as misconduct in public office, were alleged to have taken place.

Police said on Friday the Crown Prosecution Service (CPS) had advised the evidence gathered during the course of the investigation did not meet the "high bar" to prove misconduct in public office.

This means the Met will no longer be involved in investigating the betting scandal.

However, the Gambling Commission will continue its inquiries into whether confidential information was "used to gain an unfair advantage when betting on the date of the General Election", said the regulator's Chief Executive Andrew Rhodes.

The Gambling Commission continues to gather evidence and interview witnesses as part of its criminal investigation, Mr Rhodes added.

“While our involvement in the criminal investigation now ceases, it’s important that is not misinterpreted as an all clear for those whose cases were looked at," Detective Superintendent Katherine Goodwin said.

"There are still Gambling Act offences to consider and it is appropriate that they are taken forward by investigators from the Gambling Commission who have particular expertise in this field.

"Seven police officers who are alleged to have placed bets are still among those being investigated by the Gambling Commission. They also remain under investigation by the Met’s Directorate of Professional Standards."

By Anna Lamche