American intelligence documents blaming Iran for the Lockerbie bombing would have been produced in court if the Libyan convicted of Britain’s worst terrorist attack had not dropped his appeal.

Abdelbaset Ali Mohmed al-Megrahi, a former Libyan intelligence officer expected to be freed this week, had instructed his lawyers to produce internal US intelligence communications unavailable to his defence team at his trial in 2000.

The cables, from the American Defence Intelligence Agency (DIA), suggest that Iran was behind the attack on Pan Am flight 103, which killed 270 people in 1988, in response to the shooting down of an Iranian commercial airliner by the USS Vincennes, an American warship, five months earlier.

One document that the defence team had planned to produce was a memo from the DIA dated September 24, 1989. It states: “The bombing of the Pan Am flight was conceived, authorised and financed by Ali-Akbar (Mohtashemi-Pur), the former Iranian minister of interior.

“The execution of the operation was contracted to Ahmad (Jabril), Popular Front for the Liberation of Palestine General Command (PFLP-GC) leader, for a sum of 1,000,000 US dollars.

“One hundred thousand dollars of this money was given to Jabril up front in Damascus by the Iranian ambassador to Sy [ie Syria], Muhammad Hussan (Akhari) for initial expenses. The remainder of the money was to be paid after successful completion of the mission.”

The document is included in an unpublished report by the Scottish Criminal Cases Review Commission, a public body that considers miscarriage of justice claims and which had cast doubt in 2007 on the safety of Megrahi’s conviction.

The report also cites a DIA briefing in December 1989 entitled Pan Am 103, Deadly Co-operation, which named Iran as the probable state sponsor of the bombing.

Robert Baer, a retired senior CIA agent who claims that Iran was behind the attack, has alleged that the Americans were wary of pursuing the country in case it disrupted oil supplies and damaged the economy.

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