The Lockerbie bomber had £1.8m in a Swiss bank account when he was convicted eight years ago, it has been revealed.

The Crown Office, Scotland's equivalent of the Crown Prosecution Service, has confirmed it refused to grant bail to Abdelbaset Ali Mohmed al-Megrahi as recently as November last year because of concerns he might try to gain access to the money.

The existence of such a large sum in a personal account casts doubt on claims by the Libyan government that Megrahi was a low-ranking airline worker.

The disclosure also raises further questions about the wisdom of the Scottish government in releasing the bomber, who has terminal prostate cancer, on compassionate grounds in August.

Sources close to Megrahi's defence team said they were aware of the bank account and had several explanations prepared ahead of his trial in the Netherlands in 2000.

They included the claim that he had been given the money by Libyan Arab Airlines, his employer, to buy aircraft parts abroad in breach of the western trade embargo in place against his country at the time of the 1988 bombing of the Pan Am plane over Scotland, in which 270 people died.

Another explanation would have been that Megrahi had been entrusted with the funds to finance an attempt to include Libya in the Paris to Dakar rally. The issue of the account was never raised by the prosecution because it came too late to be introduced as evidence at his trial.

A source close to Megrahi said: "The crown would have said that the money was being used to buy explosives and pay bribes to people.

"It would have undermined his position as being a simple employee and that he had no big connections with anybody because someone with that status in life wouldn't have that kind of money in bank accounts."

Ben Wallace, Conservative MP for Lancaster and Wyre and a member of the Scottish affairs committee, which is inquiring into the circumstances of Megrahi's release, said the existence of the account was a "startling" revelation.

"Had this been known at the time, the financial web that linked Libya and Megrahi to international terrorism would have been a major plank in the crown's case," he said. "Far from being the wrong man, I think this suggests Megrahi was an international co-ordinator of terrorism for Libya."

Last month, The Sunday Times revealed that Megrahi was implicated in the purchase and development of chemical weapons by Libya, according to documents produced by the American government.

The papers also claimed he sought to buy 1,000 letter bombs from Greek arms dealers while working as a Libyan intelligence officer...