SCOTLAND’S top prosecutor has been on a secret mission to Libya to pave the way for more investigations into the Lockerbie bombing.

Frank Mulholland, the Lord Advocate, went to Tripoli last week with FBI director Robert Mueller to meet Libyan Prime Minister Abdurahim el-Keib and other officials, including the justice minister Ali Hamiada Ashour.

Their visit overlapped with that of Foreign Office Minister Alistair Burt, the parliamentary under secretary of state for the Foreign and Commonwealth Office.

It is understood the Libyan Transitional Government has now agreed that UK and Scottish police can begin work in the country.

A source close to the inquiry said: "The meetings with officials and ministers of the National Transitional Council are thought to have gone well and it is hoped Scottish police will soon be able to go to Tripoli."

This follows a recent announcement by Libyan interior minister, Fawzi Abdel A’al, that no treaty exists for UK police to visit Libya. He added any agreement might depend on whether Britain answered questions about its past involvement with Muammar Gaddafi’s regime.

He said Britain needed to explain the reasons for its rapprochement with the Gaddafi regime in 2004, sealed when former Prime Minister Tony Blair visited Gaddafi. Mr A’al’s views marked a significant setback in the public assurances of UK ministers and officials that detectives from Scotland and London would be allowed into Libya to investigate the Lockerbie bombing and the murder of WPC Yvonne Fletcher in 1984.

It is thought officers hope to find key documents relating to the Lockerbie bombing and hope to interview former intelligence officers.

However, a number of relatives have expressed concerns about the validity of information to be found in Libya following the overthrow of the Gaddafi regime.

A Crown Office spokesman said: "The Lord Advocate, Frank Mulholland, QC, and Robert S Mueller, Director of the FBI, met the Libyan Prime Minister to discuss the ongoing investigation into the Lockerbie bombing.

"The Libyan authorities confirmed they fully understood the importance of dealing with the tragic issues left behind by Colonel Gadaffi and his regime, both in Libya and overseas.

"The Lord Advocate expressed his desire to the Libyan Prime Minister that there will be a positive response to his request for co-operation."

A Foreign Office spokesman said: "Making progress on outstanding bilateral issues from the Gaddafi era remains a top priority. During his visit to Libya last week, the Minister for the Middle East raised these issues and had productive discussions with the Libyan justice minister and others about the Metropolitan Police’s investigation into the shooting of Yvonne Fletcher. We are now discussing with the Libyan authorities and the Metropolitan Police about taking this forward.

"The minister also discussed with Mr el-Keib the strength of the Libya-UK bilateral relationship and areas where they could further build co-operation, including health, education and training.

"He raised the importance of making progress on the investigations into the killing of Yvonne Fletcher and Lockerbie, and of taking forward reconciliation with communities affected by terrorism sponsored by the Gaddafi regime – all of which are priorities for the UK Government."