Scotland's first minister has asked for assurances that the Lockerbie bomber will be excluded from any prisoner transfer deal with Libya.
Mr Salmond said al-Megrahi's case was under appeal
Alex Salmond raised concerns that the Westminster government's position on the issue had changed.
It was reported that the UK Government drafted a transfer agreement that could cover Abdelbaset Ali Mohmed al-Megrahi.
But UK ministers have repeated that no transfer could go ahead without the agreement of the Scottish Government.
Mr Salmond spoke out on the issue after the Financial Times reported that Libya had just ratified a £450m contract with oil giant BP, after Westminster ministers drafted a prisoner transfer agreement that it claimed could cover al-Megrahi.
However BP has stressed that the £450m exploration contract, originally signed in May 2007, was a commercial one.
Mr Salmond described the report as "a very serious allegation", but said it was up to the UK Government to explain.
He pointed out al-Megrahi's case was under appeal and that the judicial process must be allowed to take its course.
The Libyan is serving life for killing 270 people in the 1988 bombing.
He was convicted in 2001 of blowing up Pan Am flight 103 over the Scottish town of Lockerbie.
Mr Salmond told BBC Scotland: "My role, the role of the government is to defend the integrity of the judicial system in Scotland and that's exactly what we intend to do."
"We've made it quite clear that, in terms of prisoner transfer agreement with Libya, we thought it would be appropriate if anyone connected with the Lockerbie atrocity was excluded specifically from any prisoner transfer agreement.
"Until very recently, that was also the position of the UK Government."
Mr Salmond went on: "Now that seems to have changed and it's up to the UK government to explain why that position has changed and why that exclusion hasn't been gained."
The UK justice department said any decision on the transfer of al-Megrahi to Libya was a matter for the Scottish legal system and stressed that no transfer could go ahead without the agreement of the Scottish Government.
A BP spokesman added: "We are a commercial company and have signed a deal that has now been ratified by the Libyan Government.
"Any matters relating to political issues should be referred to the governments concerned."
A row previously broke out between UK and Scottish ministers after former Prime Minister Tony Blair and Libyan leader Colonel Gaddafi signed a memorandum of understanding on prisoner transfer.
Downing Street said at the time that the agreement did not cover Megrahi, but UK Justice Secretary Jack Straw later said the fate of the bomber was a "matter for discussion" with Holyrood ministers.