Britain's former top IRA spy was last night making a fresh bid to start a new life, after being cleared by a jury at Newcastle Crown Court, of trying to pervert the course of justice.

Mr Martin McGartland, 27, who has lived under the name of Martin Ashe for the last six years, had claimed he was in fear of a terrorist death squad when he used duplicate driving licences to avoid a ban.

The jury took just 10 minutes to find the author of Fifty Dead Men Walking, which is fast becoming a best seller, not guilty at the end of a five-day trial.

Later, it was made clear he would be moving away from Tyneside, and the legal firm which represented him issued a statement criticising the moves which brought him to court and exposed him to danger from the IRA.

It read: ''It is Mr McGartland's view that the prosecution should never have been brought in light of his services to the public in Northern Ireland.

''The prosecution has exposed him to further danger, which his resettlement on the mainland was meant to avoid.

''Mr McGartland believes that the prosecution was brought with total disregard for his own safety, and that the Crown showed no insight into the real and imagined dangers encountered by those living in the shadow of the IRA.''

The trial took place in secret after his barrister, Mr Glen Gatland, applied to Judge Denis Orde to make an order banning publication of proceedings until the end, as it was feared the IRA might try to target the court.

During the trial the court was told that after fleeing Ulster, where it is claimed he helped save 50 lives by passing on secrets to the police, he became convinced he was being followed by potential assassins.

Almost every time he speeded away to elude them he was stopped by police, and he used duplicate driving licences to escape a ban after totting up 12 speeding points in the summer of 1993. He could not reveal to police his reasons, as he feared detection.

Magistrates thought he only had three points each time he appeared in court, because he handed in different licences. He was, however, on the verge of losing his licence under the totting-up procedure, and has since served a six-month ban.

While in operation in Ulster, he was known as Agent Carol, and the information he passed on was from top level IRA sources, and was thought to have prevented numerous bombings and shootings, and exposed arms and explosives caches.

Former Ulster intelligence gathering chief, Superintendent Ian Phoenix, who died in the Chinook helicopter crash on the Mull of Kintyre, was said to have rated him as the most successful double agent he had known.

Eventually, Mr McGartland's cover was blown and he was seized by IRA gunmen in August 1991, after helping the security forces for four years.

He managed to escape from a third storey window, suffering serious head injuries which left him with partial brain damage.He was then given a new identity and relocated by Special Branch.

Mr McGartland has taken action against Northumbria police after learning his new name and real name were being held on file. This led to a computer programmer being sacked from the force.