Politician Tommy Sheridan said he does not believe security services had anything to do with bugging his car.
Socialist politician Tommy Sheridan said he had been told by police the alleged surveillance device discovered in his car was "viable".
He dismissed speculation he was being monitored by the authorities as "garbage".
The leader of Solidarity told a news conference that the device, which could transmit audio, would be sent for further tests.
The left-wing MSP disclosed that the police believed the device found in his silver Honda Civic was wired for pictures as well as sound.
Mr Sheridan said a letter he received, tipping him off about the device, would also be sent for DNA-testing.
Mr Sheridan, leader of the Solidarity Party, said he was "concerned and worried" about the find.
He said he had wanted to show the letter but was told not to by police.
He called in police after a member of his staff found what they thought was a piece of eavesdropping equipment in the car.
Police went to the Scottish Parliament building in Edinburgh to take the car and the device away for examination.
'Communicate visually'
Mr Sheridan said he was meeting Lothian and Borders Police, who kept his car overnight and are sweeping it for bugs.
He said: "The reason they have kept it is that there is an indication that the device they have found can communicate visually as well as by audio.
"I certainly don't think that the security services are involved.
"Any speculation around that is garbage."
The MSP won a high-profile libel victory over the News of the World last year after it printed allegations about his sex life.
Prosecution authorities later instructed police to investigate allegations of perjury by witnesses during the trial.
The newspaper is seeking to overturn the verdict after being ordered to pay Mr Sheridan £200,000 damages and its appeal is set to be heard in December.
