London  - The British government was warned by Libya that the possible death in prison of freed Lockerbie bomber Abdel Basset al- Megrahi would be "catastrophic" for relations, documents about the controversial release showed Tuesday.

The claim was made by a top Libyan official who said he was assured by a British minister that neither Prime Minister Gordon Brown nor Foreign Secretary David Miliband wanted al-Megrahi to "die in prison."

The 57-year-old former Libyan intelligence agent was freed from jail in Scotland on health grounds on August 20, prompting condemnation from the White House and an outcry from relatives of the victims of the bombing.

The majority of the 270 victims of the December 1988 bombing of a Pan Am airliner over the Scottish town of Lockerbie were US citizens.

Al-Megrahi, the only person to be convicted of the attack, was given a life sentence of a minium of 27 years by a special court in 2001.

The new claims emerged in correspondence relating to the case published by the British government and the regional government in Scotland, which London hoped would defuse persistent speculation that business interests and political pressure were behind the release.

The government in London has insisted that the Libyan warning did not influence the decision that al-Megrahi should be freed, saying it was a decision for the Scottish government alone to take.

A jubilant reception for the prisoner on his return to Tripoli added to Anglo-American tensions over the affair.

Documents published by the Scottish Executive on Tuesday showed that al-Megrahi's release was top of the agenda during a visit to Libya in February of Bill Rammel, a state secretary in the Foreign Office in London.

A month later, according to the documents, Libya's minister for Europe, Abdulati Alobidi, told officials in Scotland that Rammel assured him that neither Brown nor Miliband wished al-Megrahi to die of cancer in prison.

"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," the minutes said.

Rammel had also made clear that the decision was one for the Scottish government alone.

Rammell responded to the claim Tuesday, saying only that he had made clear in all his dealings with Libya that the decision on Megrahi was exclusively one for Scottish ministers.

Eight letters published by the government Tuesday in London relate to a prisoner transfer agreement (PTA) signed with Libya in 2007.

They showed that British Justice Secretary Jack Straw wrote to Scottish leader Alex Salmond in November 2008 pointing out Libyan "concerns for health and possible return to Libya" of al-Megrahi.

However, Straw also stressed that the question of a possible release was a matter for the Scottish administration alone to decide.

The letters showed that Straw changed his mind about excluding al- Megrahi from the PTA as that could risk harming relations with Libya.

After initially agreeing that the PTA should not include anyone connected with the bombing, Straw decided later that it was in Britain's interests that the agreement took "standard form" - with no exclusion.

In the event, al-Megrahi was was allowed to return to Libya on compassionate grounds, making the use of the PTA redundant.

Britain's Conservative opposition leader, David Cameron, said the Brown government now stood accused of "double dealing."

"The British prime minister has got to be straight with the British people," Cameron said. "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." (dpa)