LONDON - British Prime Minister Gordon Brown said on Wednesday that his government had put no pressure on Scotland to release the Lockerbie bomber early to improve Britain's trade links with Libya.

Brown said he had made it clear to Libyan leader Muammar Gaddafi that it was up to the Scottish government to decide whether to free Abdel Basset al-Megrahi, who is dying of cancer. Scotland has its own judicial system and sets its own policy.

On our part, there was no conspiracy, no cover-up, no double-dealing, no deal on oil, no attempt to instruct Scottish ministers, no private assurances by me to (Libyan leader) Colonel (Muammar) Gaddafi, Brown said at an employment summit in Birmingham, central England.

Megrahi is the only person to have been convicted over the deaths of 270 people in the bombing of a Pan Am passenger plane over the Scottish town of Lockerbie in 1988. Scotland freed him on compassionate grounds last month.

Megrahi's release angered the U.S. government and many relatives of the victims and triggered accusations that Britain had put pressure on the Scottish government to release Megrahi to help British companies secure trade deals with Libya.

Opposition Conservative leader David Cameron, who leads in the polls less than a year before an election, said Megrahi should not have been freed.

He accused the British government of a catastrophic misjudgment and said there should be an inquiry into the facts surrounding Megrahi's release.

We are now in a shambolic situation where the government has upset one of our most important allies, Cameron told BBC radio. They stand accused of double-dealing, saying one thing to the Libyans and something else to the Americans.

British Foreign Secretary David Miliband said Britain had told Libya it did not want Megrahi to die in prison, but he denied putting pressure on the Scottish government.

We did not want him to die in prison. No, we weren't seeking his death in prison, Miliband told BBC radio. At every stage we said this is a matter for the Scottish government.

Documents released by the Scottish government showed Libyan officials had warned London that the death of Megrahi in a Scottish prison would have catastrophic effects for the relationship between Libya and Britain.

Brown has condemned the rapturous welcome given to Megrahi on his return to Tripoli, but has not said whether he agreed with the decision to free him.

Pictures of Megrahi's arrival were projected onto a giant screen in Tripoli on Tuesday during celebrations to mark the 40th anniversary of Gaddafi's bloodless coup in 1969.

(Editing by Tim Pearce)