Six grounds on which Megrahi could have been the victim of a miscarriage of justice were published for the first time by The Herald and Sunday Herald earlier this year.

The full report by the Scottish Criminal Cases Review Commission (SCCRC) was made public following permission from Megrahi himself.

The SCCRC findings, kept secret for five years, allowed Megrahi to proceed to appeal his conviction, but the Libyan national dropped all outstanding legal action in a bid to maximise his chances of release from Greenock Prison.

Such a move would have been necessary to secure his return home under a Prisoner Transfer Agreement, but not for the compassionate grounds route approved by Justice Secretary Kenny MacAskill.

The six grounds noted by the SCCRC included an unreasonable verdict due to uncertainty over the date on which Megrahi was supposed to have bought clothes in Malta that were found among the plane debris.

Shopkeeper Tony Gauci claimed Megrahi visited his shop, Mary's House, on December 7, 1988, but an early statement given by Megrahi – and not tested in court – found he could have been in Malta on that date, and the night before the bombing, to meet a woman friend.

The date on which the clothes were bought formed the basis of a separate ground of undisclosed evidence and a further ground of new evidence.

Mr Gauci said Megrahi resembled the man who bought clothes in his Malta shop but the SCCRC also reported undisclosed evidence concerning the identification.

The commission found Mr Gauci had a magazine with a picture of Megrahi stating he was the Lockerbie bomber three days before an ID parade in the Netherlands.

The SCCRC also raised undisclosed evidence concerning Mr Gauci's interest in financial rewards. The witness and his brother Paul received at least $3 million (£1.88m) from US justice officials after the trial.

The defence at the trial did not know he had discussed and shown an interest in reward money before identifying Megrahi. If they had, they could have challenged the credibility of the prosecution case.

The SCCRC report said: "Such a challenge may well have been justified and in the commission's view was capable of affecting the course of the evidence and eventual outcome of the trial."

This sixth ground of appeal related to undisclosed secret intelligence documents, which remain a secret.

Since the SCCRC report was made public, further information has come to light. Earlier this month, Chief Constable Pat Shearer admitted details of a break-in at Heathrow Airport, on the night the bomb might have been planted, were withheld by police for a decade.

Megrahi's first attempt at appealing his conviction was rejected in 2002.