A Scottish Government source said Justice Secretary Jack Straw spoke to his opposite number north of the border, Kenny MacAskill, and told him Abdelbaset al-Megrahi would not be excluded from a Prisoner Transfer Agreement (PTA) expected to be finalised soon.

Mr Salmond said he was "deeply disappointed" by the development, which comes just days ahead of the 19th anniversary of the 1988 outrage.

Al-Megrahi, who is serving life in Greenock Prison, is currently pursuing a second appeal against his 2001 conviction for bombing Pan Am Flight 103 over the Scottish town of Lockerbie on December 21 1988.

Former prime minister Tony Blair signed a memorandum of understanding during a visit to Libya in May this year, kicking off negotiations on an agreement allowing the transfer of prisoners between the justice systems of the two states.

But Downing Street said then that the memorandum did not cover the al-Megrahi case, and that any future transfer involving him would anyway be a devolved matter for Scottish authorities - effectively granting Holyrood a veto on his return home.

The Foreign Office has said discussions on the proposed PTA were continuing and no agreement had been reached.

And a spokeswoman for the Ministry of Justice pointed out that, under the terms of PTAs in force between the UK and 97 countries worldwide, prisoners can only be transferred where both Britain and the receiving state agree to the move.

But Mr Salmond said it was not good enough to assume that any proposed transfer for al-Megrahi would be blocked by ministers in London or Edinburgh.

He insisted a specific measure should be included in any agreement with Tripoli, excluding any individual convicted of involvement in the Lockerbie bombing from being transferred.