Libyan Abdelbaset al-Megrahi is the only person to be convicted of the bombing of Pan Am flight 103 over Scotland in which 270 people were killed more than 25 years ago.
Megrahi, who was released from jail by the Scottish government on compassionate grounds after being diagnosed with prostate cancer, died in 2012 protesting his innocence and his family plan to appeal against his conviction.
But former Iranian intelligence officer Abolghassem Mesbahi has told an Al Jazeera documentary that the bombing was ordered by Tehran and carried out by the Syrian-based Popular Front for the Liberation of Palestine-General Command (PFLP-GC) in retaliation for a US navy strike on an Iranian commercial jet six months earlier, in which 290 people died.
The US ship apparently mistook the plane for an F-14 fighter jet.
Speaking to Al Jazeera, Mr Mesbahi said: "Iran decided to retaliate as soon as possible. The decision was made by the whole system in Iran and confirmed by Ayatollah Khomeini.
"The target of the Iranian decision makers was to copy exactly what's happened to the Iranian Airbus. Everything exactly same, minimum 290 people dead. This was the target of the Iranian decision makers."
US Defence Intelligence Agency cables at the time reported that the leader of the PFLP-GC had been paid to plan the bombing, the broadcaster said.
The Crown Office has previously said the alleged involvement of the PFLP-GC was addressed at the original Lockerbie trial.
A successful application from Megrahi's family to the Scottish Criminal Cases Review Commission (SCCRC) could start the third appeal into the conviction.
Megrahi lost his first appeal in 2002, one year after he was found guilty of mass murder and jailed for life.
The SCCRC recommended in 2007 that Megrahi should be granted a second appeal against his conviction. He dropped his appeal two days before being released from prison in August 2009 on compassionate grounds.
In December, the Libyan attorney general announced he had appointed two prosecutors to work on the case. For the first time they met Scottish and US investigators who are trying to establish whether there are other individuals in Libya who could be brought to trial for involvement in the attack.
The Crown Office said there was "nothing new" in the claims.
A spokesman said: "Mesbahi's claim that Iran was responsible was first reported in the media in the late 1990s and was available to the defence before the trial but they did not call him as a witness.
"The wider alleged involvement of the PFLP-GC has been repeatedly reported over many years but was addressed in full and rejected at the original trial.
"The only appropriate forum for the determination of guilt or innocence is the criminal court, and Mr Megrahi was convicted unanimously by three senior judges. His conviction was upheld unanimously by five judges, in an Appeal Court presided over by the Lord Justice General, Scotland's most senior judge.
"As the investigation remains live, it would not be appropriate to offer further comment."