The original suspect in the Lockerbie bombing does not have immunity from prosecution and could be charged with mass murder, it emerged yesterday.

Mohammed Abu Talb, a Palestinian now serving a life sentence in a Swedish jail for other explosive offences, was the chief suspect for the attack on PanAm flight 103 until 1990, when Libya became the focus of the inquiry.

He served as a prosecution witness at the trial of Abdelbaset Ali Mohmed al Megrahi at Camp Zeist in the Netherlands and there was a widespread belief he had been granted Crown immunity. Lawyers involved in the case and relatives of victims had all been told Abu Talb received Crown protection for agreeing to give evidence.

However, The Herald can reveal today that Talb is not immune from prosecution and could therefore be tried for the atrocity if Megrahi is cleared, after the Scottish Criminal Cases Review Commission gave him leave to mount a second appeal against his conviction. A spokeswoman for the Crown Office confirmed: "Abu Talb does not have Crown immunity."

The commission is understood to have uncovered new evidence which strengthens the line of inquiry against Abu Talb, who was allegedly funded by Iran to explode the plane in revenge, after the American cruiser USS Vincennes shot an Iran Air flight out of the sky on July 3, 1988, killing 290 people.

The SCCRC's report refers to the recovery of new official records from various organisations in Italy, which are thought to refer to Abu Talb, who travelled between Cyprus, Rome, Malta and Frankfurt in the run-up to the bombing.

Evidence not heard at the original trial in 2000-1 also reveals the CIA thought Abu Talb was the man responsible and that the police found clothes, including a blue babygro similar to the one found at Lockerbie, when they raided his flat in Germany.

Robert Black, QC, a lawyer instrumental in arranging for the case to go ahead at Camp Zeist, said yesterday: "Abu Talb and the Iranians could form part of a new case. If there is genuinely new evidence, it seems to me that would satisfy the case for a new trial. In legal theory, there is no reason why they could not bring charges against someone else."

Tam Dalyell, the veteran campaigner for justice over Lockerbie, added: "This is of high potential significance.

I was at Zeist when Abu Talb appeared and I cannot imagine why he was not pressed more closely."

Jim Swire, whose daughter, Flora, died in the tragedy, said: "This is excellent news and opens up all sorts of avenues for the future. I have always been under the impression that Abu Talb had immunity.

"The SCCRC has said that the court was not justified in accepting that the clothes were bought (in Tony Gauci's shop) on December 7. They chose the least likely day when, in fact, the most likely day the clothes were sold - in line with the Christmas lights and weather - was in November, when Abu Talb was in Malta."

Eddie MacKechnie, Megrahi's solicitor between 2001 and 2006, had also been led to believe that Abu Talb was immune from prosecution. At Camp Zeist, defence counsel alleged the Syrian-backed Popular Front for the Liberation of Palestine- General Command (PFLP-GC) and the lesser-known PPSF were responsible for the Lockerbie bombing. They claimed Abu Talb was linked to both terrorist groups.

In his testimony, Abu Talb told the court that he was not involved in the 1988 Lockerbie bombing and that he ended "all activities relating to Palestine at the end of 1982". However, he was jailed for life in 1989 for the bombing of a Danish synagogue in 1985.

Hans Kochler, the independent UN observer, last night reiterated calls for a full independent inquiry to investigate who was responsible for Lockerbie and how the case was mishandled, in his view, by the Scottish judiciary and officials in the UK and US.

The main ground for Megrahi's appeal is likely to be new evidence which undermines the credibility of Gauci, the key Crown witness, who claimed Megrahi bought clothes found in the aircraft wreckage from his Maltese shop on December 7, 1988.

Gauci claimed it was raining when "the man" bought the clothes but meteorological records indicate there was no rain on December 7.

The Maltese shopkeeper saw a photograph of Megrahi in a magazine article linking him to the bombing just four days before he picked out the Libyan at an identity parade.