Lord Fraser, the former lord advocate who charged the man convicted of the Lockerbie bombing, has revealed he was unaware that evidence presented at his trial seems to have left Britain beforehand.

The Tory peer has told a television documentary that he did not know that a fragment of circuit board linked to the bomb had allegedly been moved to an FBI lab in Washington for analysis ahead of the trial and conviction of Abdelbaset Ali Mohmed al-Megrahi.

Fraser said he would not have agreed to the step because it could have left the crown open to accusations at the trial that the circuit board could have been damaged or tampered with during the move.

The original trial heard the fragment was found in a piece of recovered clothing in a wood 25 miles from Lockerbie, six months after the bombing in December 1988.

Prosecutors linked it to Megrahi after Thomas Thurman of the FBI identified it as part of a sophisticated timer used to detonate explosives. He said it was made by Mebo, a Swiss firm which supplied the component only to Libya and the East German Stasi.

Fraser’s comments were made in a Dutch documentary called “Lockerbie Revisited”. His comments come as Megrahi is appealing against his conviction for the murder of 270 people in Britain’s worst terrorist attack. It will be for the Appeal Court to determine the significance of the alleged movement of the fragment in 1990, which may form part of Megrahi’s appeal.

The Libyan authorities have asked Scottish ministers to transfer Megrahi to their custody under the terms of a transfer deal brokered by London and Tripoli, but a condition of the treaty is that prisoners cannot leave the country while criminal proceedings are ongoing.

Megrahi, who is terminally ill with prostate cancer, has revealed that he does not believe he will live to clear his name. He said he may drop his appeal to try to spend his final days with his family.

The Libyan said it had always been his intention to remain in Scotland to prove his innocence but he does not believe he has that chance any more. This is because a successful appeal would lead to his conviction being quashed rather than declaring him not guilty.

He said his low spirits as a result of being away from his wife, children and parents, were reducing the chances of his body responding to medical treatment and that there was now little to keep him here.

He made his views known last week in a meeting with Christine Grahame, the nationalist MSP, who has taken an interest in his case. He told her he was happy for his views to be publicised although his lawyer has stipulated that he cannot be directly quoted.

Megrahi believes he will die by the end of the year, long before his appeal is expected to conclude and complains that prison is reducing his lifespan. He claims his isolation and depression are reducing the chance of his body responding to the medical treatment he receives. If your mood is low the body will not respond properly to medication to fight the disease, he told Grahame.

There is no consideration in the criminal justice system for his health, Megrahi said. People do not care about his condition and the system is unfair, he added.

The Scottish prison service says it always provides seriously ill prisoners with support.

Megrahi regards as perverse the fact that his transfer to Libya would not be guaranteed even if he agrees first to drop his appeal, but he feels he may have to take the gamble.

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