Police Scotland is close to ending a two-year probe in to allegations of criminality by Lockerbie investigators and prosecutors.

In an unusual move, the national force has has appointed an independent QC to advise it on the inquiry because it could not ask Crown lawyers to assess evidence of alleged wrongdoing against the Crown.

Detectives are investigating nine allegations made by the Justice for Megrahi or JFM group, who believe that the only man ever convicted of the 1988 bombing, Abdelbaset al-Megrahi, was the victim of a miscarriage of justice.

Mr Megrahi died in his native Libya in 2012 protesting his innocence despite his 2001 conviction at a specially convened Scottish court in the Netherlands.

Crown officials have stressed that the Lockerbie case remains live and that they have not ruled out further prosecutions.

Police Scotland has been looking in to the JFM allegations since February 2014 under Operation Sandwood. The campaign group has been lobbying for an independent prosecutor to investigate. The Lord Advocate, Frank Mulholland, has previously said he will appoint a QC to deal with any report from the police. This person would not be the same person as the senior advocate advising the police.

Deputy Chief Constable Iain Livingstone has now written to the Justice Committee of the Scottish Parliament confirming progress.

He said the allegations were "diverse in nature, resulting in a protracted inquiry".

Mr Livingstone added: "It has required a detailed and methodical approach, to ensure the necessary rigour to investigate the matter of complexity and sensitivity raised.

"As a result the investigation has taken longer than initially assessed.

"I can nevertheless confirm that the investigation has entered its final phase. A detailed report will be submitted by the senior investigating officer to me within the next two months.

"To ensure the critical requirement of demonstrating independence from the Crown, the report will be scrutinised by the independent Queen's Council appointed by Police Scotland."

Detective Superintendent Stuart Johnstone, Senior Investigating Officer for Operation Sandwood, said:

"The Operation Sandwood enquiry into nine allegations by the Justice for Megrahi group is still ongoing; it started in February 2014.

"The operation is reaching its final stages and is being dealt with as a major investigation by Police Scotland.

"A draft report is in the progress of being compiled, drawing on the findings and conclusions of two years of detailed examination and investigation.

"To ensure the critical requirement of demonstrating independence form the Crown, the report and its findings will be scrutinised and assessed by the independent Queen’s Counsel appointed by Police Scotland to provide independent direction and advice."