Crash investigators search the area around the cockpit of Pan Am flight 103 in a farmer's field east of Lockerbie Scotland after a mid-air bombing killed all 259 passengers and crew, and 11 people on the ground. Picture taken December 23, 1988. REUTERS Muammar Gaddafi's Libyan regime was publicly blamed by the US for the attack

The CIA secretly held Syrian militants, rather than Libya, responsible for the Lockerbie bombing, according to newly unearthed testimony from a former US spy in the Middle East.

Dr Richard Fuisz said in a sworn deposition in 2001 that he was told by up to 15 senior Syrian officials that the Popular Front for the Liberation of Palestine-General Command (PFLP-GC) had carried out the attack.

He also testified that CIA bosses told him the PFLP-GC was responsible, according to a lawyer's note of a second deposition. Ahmed Jibril, the group's founder leader, who is still alive at 75, was singled out as being to blame for the downing of Pan Am flight 103 over Scotland in December 1988, killing 270 people.

"Numerous high officials in the Syrian government were quite affirmative on Jibril's involvement in Pan Am 103," Dr Fuisz told lawyers, during his deposition in Virginia in 2001.

Dr Fuisz gave his depositions in 2000 and 2001 at the request of Megrahi's defence lawyers. However, the evidence came too late to be used in the trial. They were first published by Channel 4 News. The CIA declined to comment.

Muammar Gaddafi's Libyan regime was publicly blamed by the US for the attack, and Abdelbaset al-Megrahi was convicted of the bombing in 2001. He was later released and died last year in Libya.

But serious doubts about the conviction have been raised by investigative journalists for several years, centring on forensic evidence, and Libya has strenuously denied involvement.

The PFLP-GC were in fact the first prime suspects in the investigation.

Experts suggested it may have been ordered by the Iranian government as revenge for the accidental shooting down of an Iranian passenger jet by a US battleship months earlier, killing 290.

They added that blame may have been diverted from Iran in order to protect secret and delicate negotiations by George Bush's US administration over western hostages.

Dr Fuisz, a businessman who is said to have been a senior US intelligence asset in the Middle East in the 1980s and 90s, said that the Syrian officials he spoke to interacted with Jibril "on a constant basis" and that he was widely regarded to be the mastermind behind the bombing.

Asked who the Syrian officials cited as their source for the information, he said: "My recollection is they were direct. They were not hearsay sources on their part." Asked if that he understood that to mean that he was "being told by members of the Syrian government that Jibril, and or members of the PFLGC were taking credit for the bombing," he replied: "Yes".