The defence team of the man convicted of the Lockerbie bombing yesterday demanded official documents that were not disclosed at the original trial.

The non-disclosure by prosecutors could indicate Abdelbaset Ali Mohmed al Megrahi, the man convicted of the 1989 bombing that killed 270 people, suffered a "miscarriage of justice", a court was told yesterday.

The news comes a week after The Herald revealed that these secret documents, vital to unearthing the truth about the Lockerbie bombing, had been obtained by the Crown Office but never shown to the defence.

The Scottish Criminal Cases Review Commission (SCCRC) team that investigated Megrahi's conviction is understood to have discovered the existence of a document about the MST13 timer which allegedly detonated the bomb over Lockerbie in 1988.

Using its enhanced powers, the commission compelled the Crown to show it the highly confidential document and decided the contents - still unknown to the defence - were sufficiently important for a court to have believed the conviction could have been a miscarriage of justice.

Proving the MST13 timer found at the site was purchased by the Libyans was pivotal to the conviction at Camp Zeist in the Netherlands. It had been thought that the document came from the CIA but yesterday the Crown revealed it was from "another" foreign country.

The defence team yesterday lodged a court order to force the Crown to disclose the documents. The Crown agreed to respond to the demand within the next six weeks, either with copies of the documents or their reasons for not doing so.

Yesterday's hearing in Edinburgh marked the first time the case has returned to court since Megrahi was granted the right to a second appeal in June.

The SCCRC, which spent more than three years investigating the Libyan's conviction, referred the case back to the Scottish courts on six separate grounds, including non-disclosure.

Maggie Scott, Megrahi's QC, said the defence was seeking two documents, one of which relates to the supply of timers.

She said she could not understand why the Crown needed more time, having learnt of the commission's views in June.

She said: "I can advise the material was originally provided to the UK Government by the government of another country. It is clear to me that the Crown are not yet prepared to release these documents. It is not at all clear to me what the basis is for the refusal."

Ronnie Clancy, QC, the advocate-depute, said the documents were handed over to prosecutors on the basis that they remained confidential.

He said: "The documents in question were passed to the UK Government on the basis that they were regarded as being confidential by the authority that passed them over.

"That being so, the Crown has always taken the position that, if possible, confidentiality should be respected and there are public interest considerations in regard to keeping the confidentiality of information that comes from a foreign source."

Megrahi - the only man convicted of the bombing after his co-accused was acquitted - is serving a 27-year sentence in HMP Greenock. He was not present at yesterday's hearing before three judges.

Jim Swire, whose daughter Flora was one of the Lockerbie victims, was at the hearing.

"I am disappointed that the proceedings are clearly going to take so long, but we have to give the Crown and the defence time to prepare the case to ensure justice is done," he said.