British film-makers Bill Cran and Christopher Jeans, who have spent the last three years investigating the Lockerbie bombing, were given access to the defence material by Megrahi, who hired a former Manhattan District Attorney to review his case and gather new evidence.

Megrahi’s conviction was based on the theory that Colonel Gaddafi personally ordered the terrorist attack in retaliation for the 1986 US bombing of Tripoli and Benghazi, in which Gaddafi’s daughter was killed.

But the documentary claims that it was in fact an act of revenge for the loss of Iran Air flight 655 in July 1988, which was accidentally shot down by the USS Vincennes in the Persian Gulf.

Mr Mesbahi, who once reported directly to former Iranian president Akbar Hashemi Rafsanjani and now lives under a witness protection programme after defecting to Germany in the late 90s, told Al Jazeera: “Iran decided to retaliate as soon as possible. The decision was made by the whole system in Iran and confirmed by Ayatollah Khomeni.

“The target of the Iranian decision-makers was to copy exactly what happened to the Iranian Airbus. Everything exactly the same, minimum 290 people dead.”

The documentary claims the Lockerbie bombing was arranged during secret meetings in Malta attended by members of the Iranian, Syrian and Libyan regimes, leaving open the possibility that Libya did play a part in the bombing.