The document, which was drawn up in March 1991, eight months before two alleged Libyan agents were charged with the bombing, says that Ali Akbar Montashemi, the former Iranian interior minister, paid $10m (£6.5m) to terrorists who carried out the attack on Pan Am Flt 103 in December 1988. The declassified US Defense Department paper, obtained by lawyers for Pan Am, is the first official evidence which challenges the British and American assertion that Libya acted alone.
The claims have revived suspicions that Iran ordered the bombing in revenge for the shooting down of an Iranian airbus by the USS Vincennes in July 1988. Iran is thought to have commissioned a Syrian-backed terror group, the Popular Front for the Liberation of Palestine General Command, to carry out the attack.
British officials said the leaked document was based on "dud intelligence", and insisted that Colonel Gaddafi, the Libyan leader, should hand over the two suspects, Abdel Basset Ali Al-Megrahi and Lamen Khalifa Fhimah, for trial in Scotland or the US.
The Crown Office in Edinburgh, which brought the charges against the two Libyans, dismissed the allegations as "an old story" which could not be substantiated. In Washington, the U.S. Air Force discounted the document as a "raw" field intelligence reportbased on second or third-hand information gathered from defecting Iranian pilots. The Tory MP Sir Teddy Taylor has tabled a Commons question asking when Douglas Hurd, the Foreign Secretary, was informed about the claims of Iranian involvement. Mr Taylorsaid yesterday if the Government had been told of the findings in March 1991, its explanation of the Lockerbie bombing was "unbelievable".