A string of high profile British witnesses who refused to testify at a US Senate hearing into the release of the Lockerbie bomber were today facing accusations of "stonewalling".
The US Senate Foreign Relations Committee postponed tomorrow's hearing after key witnesses including former Justice Secretary Jack Straw, Scottish Justice Secretary Kenny MacAskill and First Minister Alex Salmond turned down requests to attend.
Senator Robert Menendez, a Democrat who was due to chair the hearing, said "no witness of consequence has the courage" to step up and clear the air but insisted it will be held "in the near future".
He said: "It is utterly disappointing and I think pretty outrageous that none of these key witnesses will cooperate with our request to answer questions before the Senate Foreign Relations Committee. They have stonewalled."
The committee is investigating whether BP lobbied for Abdelbaset Ali Mohmed Al Megrahi's release to help get a 900 million US dollar exploration agreement with Libya off the ground.
BP acknowledged it urged the British government to sign a prisoner transfer agreement with Libya, but stressed it did not specify his case.
Mr Menendez also attacked outgoing BP boss Tony Hayward for refusing to testify, saying: "It is apparently more important to BP and Mr Hayward to focus on his multi-million dollar golden parachute than to help answer serious lingering questions about whether the company advocated trading blood for oil."
He spoke after the UK Government said yesterday that "significant lessons" were learned in relations with Scotland after the row over the freeing of Megrahi.
In a response to a recent Scottish Affairs Select Committee report into relations between the two administrations, the Tory-Lib Dem coalition said it wants to build more "positive relations" with Edinburgh.
"We believe that there are significant lessons from this disagreement that have already been learnt," the UK Government response said.
"The Government's priority is to build more positive relations with the Scottish Government in all areas."
The SNP government clashed with the previous Labour administration at Westminster over a controversial "deal in the desert" agreed with Libya three years ago without Edinburgh's knowledge.
The Memorandum of Understanding paved the way for a prisoner transfer agreement (PTA), which Megrahi unsuccessfully applied for to Scottish ministers.
The response states: "In future the Government will consider carefully the appropriate balance between interests of confidentiality and the responsibility to keep the Scottish Government informed of international agreements made on its behalf.
"This includes consultation with the devolved administrations on matters relating to international relations which touch upon devolved matters."
Megrahi is the only person convicted of the 1988 bombing in which 270 people were killed. He was released on compassionate grounds last July after medical evidence indicated he only had three months live.
Calls for the decision to release Megrahi to be re-examined grew in volume in the wake of the Gulf of Mexico oil spill and revelations that BP lobbied for the PTA, amid concern that ditching it could damage an exploration deal it signed in Libya.
Foreign Secretary William Hague described Megrahi's release as "wrong and misguided" at the weekend.
Jim Swire, whose daughter Flora died in the crash, said today that the US senators were looking at links between BP's commercial interest in Libya and the return of Megrahi.
"That's a question that if anyone from Britain could address, it would be people from Westminster," Dr Swire told BBC Radio Scotland.
"People have forgotten that there is no real link between his release and the so-called 'deal in the desert', because Kenny MacAskill and Alex Salmond didn't want to touch the prisoner transfer agreement which was set up in the deal in the desert."
Megrahi was eventually freed under compassionate release after medical evidence indicated the bomber had three months to live.
Dr Swire believes that Megrahi has been the victim of a miscarriage of justice.
"Are we not interested that the man who has been freed by Kenny MacAskill might, in fact, not be the man who was involved in causing the tragedy?" he said.
"That seems to me over-ridingly a more important question than the question of the minutiae of why he was freed.
"I can understand why they major in on those aspects of it, but I do think it's relatively peripheral."