THE only person convicted of the 1988 Lockerbie bombing has forgiven the man whose evidence was crucial in finding him guilty, as it is claimed that previously unseen evidence would have acquitted him.

Today the official biography of the Libyan convicted of the atrocity, Abdelbaset Ali Mohmed al Megrahi, will be launched and two documentaries will be aired, all of which highlight new evidence and previously unseen documents that experts say would have overturned the conviction.

Maltese shopkeeper Tony Gauci claimed that Megrahi purchased clothes found packed around the bomb – a claim the Libyan has always denied.

In one of the TV programmes, Megrahi, 59, says: "I have never seen him in my entire life except when he came to the court. I find him a very simple man. But I do forgive him."

The Herald is one of only two newspapers in the world to have had advance access to the book, Megrahi: You Are My Jury, by John Ashton, a former member of the defence team.

The Al Jazeera documentary to be broadcast today claims Megrahi's conviction would "almost certainly" have been overturned had previously unseen evidence been used in an appeal.

The programme, Lockerbie: Case Closed, gained access to the investigations of the Scottish Criminal Case Review Commission (SCCRC) – which referred Megrahi's case for a fresh appeal in June 2007 on six grounds – and also uncovered fresh scientific evidence that it claims is unknown to the commission and "comprehensively undermines" part of the case against Megrahi.

A total of 270 people were killed when Pan Am Flight 103 exploded over Lockerbie on December 21, 1988.

Megrahi was sentenced to life imprisonment in 2001. He was released on compassionate grounds in August 2009 after he was diagnosed with terminal cancer, and returned to Libya.

Doctors estimated he had three months to live, but he is still alive.

Earlier this month, campaigners fighting on behalf of Megrahi accused politicians, lawyers, civil servants and governments of an "orchestrated desire" to keep details of his case under wraps.

Members of the Justice For Megrahi group, who have called for an inquiry into his conviction, said the Crown Office and civil service would "do anything" to stop disclosure.

The Al Jazeera documentary claims to disclose the "dramatic results" of new scientific tests that undermine forensic evidence used in the case.

John Ashton, the author of the book, has been investigating the case for nearly 20 years.

He said: "The Lockerbie disaster was Europe's worst terrorist attack. More Americans died in that attack than in any other terrorist event before 9/11. It's also Britain's worst miscarriage of justice – the wrong man was convicted and the real killers are still out there."

The programme, which will be broadcast at 8pm on Al Jazeera English, will feature an interview with Megrahi filmed in December. In an interview to be broadcast on BBC Scotland tonight, Megrahi says he has forgiven shopkeeper Mr Gauci, who was a key witness for the Crown.

Megrahi has always denied buying the clothes. In the interview, he says: "I'll tell him he dealt with me very wrongly."

Among the reasons provided by the SCCRC for a fresh appeal were inconsistencies in Mr Gauci's statements.

"Forgiving him, I am facing my God very soon," Megrahi said. "I swear I have never been in his shop or buy any clothing from his shop.

"And he has to believe this because when we meet together before God, I want him to know that before I die.

"This is the truth."

Parts of the interview will be transmitted in BBC Scotland Investigates: Lockerbie – The Lost Evidence, on BBC One Scotland tonight at 7.30pm.

The programme will include an interview with Justice Minister Kenny MacAskill, who says he stands behind the original conviction.