Tommy Sheridan said yesterday that he was “mixed-up, concerned and worried” after finding what appeared to be a viable bugging device under the back seat of his car.

The former leader of the Scottish Socialist Party said that police believed that the device, which was being examined by detectives last night, was wired for pictures as well as sound.

Mr Sheridan said that he called in police on Thursday after a member of his staff found what they thought was a piece of eavesdropping equipment in his Honda Civic. The discovery followed a letter claiming that the MSP’s car was being bugged.

Mr Sheridan said: “It was posted in Edinburgh. We have the envelope and the letter itself, and the police are going to carry out DNA sampling and other forensic examinations on the letter.”

He added: “The letter made a number of points about the idea of me being tracked and monitored. We felt it was important enough to get it checked. I contacted a security analyst and the police. Both of them searched the vehicle and they found a device.”

The bugging allegation is the latest bizarre twist in Mr Sheridan’s career. However, despite previously claiming that he was the victim of an MI5 campaign to undermine him, the MSP said that he did not believe that the security services were involved.

In a reference to the News of the World, whom he sued after it published libellous stories about his sex life, he added: “I think there is only one newspaper group in Britain today with former journalists spending time behind bars for this type of stuff.”

The newspaper denied last night that it had anything to do with the alleged bugging. A spokesman said: “Mr Sheridan’s suggestion that this newspaper is responsible for ‘bugging his car’ is without any foundation whatsoever.”

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