His release angered the US government and many relatives of the victims and triggered accusations that Britain had pushed the Scottish government to make the decision in a bid to secure trade deals with Libya.

Confidential papers

David Miliband, Britain's foreign secretary, said on Wednesday that Britain had told Libya it did not want al-Megrahi to die in jail but insisted his government had not pressured Scottish officials.

"The allegation that is being made ... is that somehow we pressured the Scottish government into making a decision one way or another," he said, adding: "There was no pressure from the British government on the Scots."

In depth

 Profile: Abdel Basset al-Megrahi
 Bomber's homecoming slammed
 Release prompts anger and relief
  Video: Al-Megrahi speaks out
  Video: Opinions divided over Lockerbie appeal
 Video: Lockerbie remembered
 Al-Megrahi statement in full

Britain released confidential papers on Tuesday on the lead-up to the prisoner's release, revealing that a British minister told Libyan officials earlier this year that Brown did not want Abdel Basset al-Megrahi to die in prison.

The letters also show that British officials repeatedly stressed the importance of growing UK-Libyan interests in pushing for the release of al-Megrahi, who was moved into an emergency room on Wednesday in a Tripoli hospital where he is undergoing treatment.

The British government released the documents in an attempt to quell speculation that it pushed for al-Megrahi's release based on moves to increase economic co-operation with Libya.

Britain has regional governments in Scotland, Wales and Northern Ireland that are responsible for local issues, but retains power over foreign policy.

According to the papers, Jack Straw, Britain's justice secretary, underscored the importance of a "strong relationship" with Libya.

"You ask what I mean by 'national interests," he said in a letter last year to Alex Salmond, the Scottish first minister.

Release condemned

"Developing a strong relationship with Libya, and helping it to reintegrate into the international community, is good for the UK.

"Libya is one of only two countries to have ever voluntarily and transparently dismantled its weapons of mass destruction programme.

Al-Megrahi wrote a letter to Scottish authorities declaring his innocence [AFP]

"Having sponsored terrorist attacks in the past, it is now an important partner in the fight against terrorism."

The release of the documents is likely to fan resentment in the US, where al-Megrahi's release, after serving eight years of a life sentence, has been vehemently condemned.

Many of the 270 people killed in the bombing were US citizens.

Commenting on the latest revelations, Richard Kolko, a spokesman for the US justice department, said that his department had "received assurances in the 1990's that al-Megrahi's full sentence would be served in Scotland".

The statement seemed to contradict other documents, including one from Britain's foreign office, that said there was no commitment given to the US to keep al-Megrahi imprisoned.

The exchanges also raise questions on whether Britain warned Scotland of a possible diplomatic fallout with the US should al-Megrahi be released.

Straw has denied that the negotiations referred to in his letters, which were leaked to a local newspaper, involved any commercial deals with Libya.