A British minister told Libya Gordon Brown did not want the Lockerbie bomber to die in a Scottish prison, according to newly released papers on the case.
The claim is contained in a Libyan version of an exchange relating to the case of Abdelbaset Ali al-Megrahi.
The then Foreign Office minister Bill Rammell has confirmed he told Libya the UK government was not "actively seeking" Megrahi's death in prison.
However, he denied having any knowledge of the prime minister's personal view.
Mr Rammell, now armed forces minister, also insisted he made clear to the Libyans during a visit to Tripoli in February this year that any decision on Megrahi had to come from Scottish ministers.
Scottish Justice Secretary Kenny MacAskill allowed Megrahi, who is terminally ill with cancer, to be freed from Greenock Prison on 20 August on compassionate grounds after rejecting his return to Libya under a prisoner transfer agreement.
Mr Brown and UK ministers have since declined to say whether they supported freeing Megrahi, stressing it was a decision for the Scottish Government.
Former Foreign Office minister Bill Rammell details his conversations with Libya
But released records of a meeting between Libyan Europe minister Abdulati Alobidi and Scottish officials on March 12 suggested Mr Brown and David Miliband, the foreign secretary, did not wish Megrahi to die in a Scottish prison.
The document said: "Mr Alobidi spoke of Mr Bill Rammell's visit to Tripoli in February and that they had discussed the matter of the prisoner transfer agreement.
"Mr Alobidi confirmed that he had reiterated to Mr Rammell that the death of Mr Megrahi in a Scottish prison would have catastrophic effects for the relationship between Libya and the UK.
"Mr Alobidi went on to say that Mr Rammell had stated that neither the prime minister not the foreign secretary would want Mr Megrahi to pass away in prison but the decision on transfer lies in the hands of the Scottish ministers."
However, when asked by the BBC if Mr Brown had told him that he did not want Megrahi to die in a Scottish prison, Mr Rammell replied: No, I've not dicsussed this with the prime minister either before the event or after.
"I was responding to a specific concern that the Libyans put to me that they didn't wish Al Megrahi to die in prison.
"In response to that in a conversation with my counterpart, I made clear that we were not actively seeking his death in prison but we emphatically, and this is what I said to him at the time, we emphatically would not intervene and it was a matter for Scottish ministers."
Conservative Leader David Cameron said the UK Government now stood accused of "double dealing", and called for an inquiry.
He said: "The British prime minister has got to be straight with the British people. For weeks he's been refusing to say publicly what he wanted to happen to Megrahi, yet we now learn apparently privately the message was being given to the Libyans that he should be released."
Other letters now made public by the UK and Scottish governments reveal UK Justice Secretary Jack Straw changed his mind about excluding the Lockerbie bomber from a proposed prisoner transfer agreement with Libya.
In a letter to Scottish ministers in September 2007, Mr Straw initially agreed it should not include anyone connected with the bombing.
But three months later he said it was in the "wider" UK interests that the agreement take a "standard form" - with no exclusion.
In a further letter to Scottish First Minister Alex Salmond, on 11 February 2008, Mr Straw said Libya had become an "important partner in the fight against terrorism" and was helping to counter illegal immigration.
The mother of one of the Lockerbie victims responded to the documents' publication by accusing politicians of putting profits before justice for terrorists.
Susan Cohen, who lost her daughter Theodora in the tragedy, said: "It's so obvious that this was something that Blair wanted, that Straw wanted and whoever else wanted. He (Megrahi) was negotiable, he was a chess piece."
Another document included a letter from Megrahi to Mr MacAskill in which he said: "I am unjustly convicted of a most heinous crime."
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John Mosey, whose daughter 19-year-old Helga was killed, said the families still needed answers about the bombing.
Mr Mosey told BBC News: "What we are forgetting is there were 270 people on that plane who have been killed and we have had no proper inquiry, no serious answers."
Minutes of a meeting on 10 August between Libyan and Scottish officials on prisoner transfer discussed concerns that the bomber could be returned to a "fanfare" in Libya.
The notes said: "Mr Alobidi said he would like to take this opportunity to assure the Scottish Government that if Mr al-Megrahi were to be transferred to Libya that it would be done quietly and peacefully and away from the glare of the media."
The subsequent hero's welcome given to Megrahi on his return, with some members of the crowd waving Saltires, has drawn much criticism.
Other letters from the Foreign Office to the Scottish Government, from July and August this year, claimed no commitment had been given to the US that Megrahi would serve out his sentence in Scotland.
Megrahi was released from a life sentence imposed for his part in the bombing of Pan Am flight 103 over Lockerbie in December 1988.
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