The defence team for the man convicted of the Lockerbie bombing should get limited access to a confidential document providing national security is not put at risk, Scottish prosecutors said yesterday.

The Crown Office move appeared to differ from the position of the Advocate General, who represents the UK Government and has said that disclosure would cause "real harm".

Ronald Clancy, QC, told three appeal judges that the Crown would be prepared for Abdelbaset Ali Mohmed al Megrahi's lawyers to see a "summarised or redacted" version of the material.

At the Court of Criminal Appeal in Edinburgh, Mr Clancy acknowledged that the Advocate General Lord Davidson, QC, may be "less enthusiastic" about partial disclosure.

But he added: "Limited disclosure by way of a summarised or redacted version, or for that matter both, is the best option if this can be given to the petitioner without damaging the national security interests which give rise to the plea."

The document, which is thought to contain information about the electronic timer used to detonate the bomb, was uncovered by the Scottish Criminal Cases Review Commission.

The commission concluded that failure to disclose the document could constitute a miscarriage of justice, resulting in the case being referred back to the courts for a second appeal.

Megrahi's defence team is arguing that they need "full disclosure" of the document "in order to exercise his right of appeal".

But Foreign Secretary David Miliband has signed a certificate of "public interest immunity", claiming that disclosure would cause "real harm" to national security and international relations.

Yesterday was the second day of a hearing to decide the procedure for a future hearing on whether to grant the defence team access to the document.

The Crown Office and Advocate General have said that judges will have access to the full document, but they want a closed court hearing to discuss the issues surrounding its disclosure.

Mr Clancy said that if full disclosure was not granted, special security-vetted counsel should be appointed to replace the defence team in the hearing. He admitted that the use of special advocates, who would in this case represent the interests of Megrahi, was "unchartered territory" in Scotland.

Margaret Scott, QC, for the defence, told the court that she did not object in principle to a closed hearing nor to the appointment of a special advocate. The hearing continues today.