The man convicted of the Lockerbie bombing has signed a secret document agreeing to drop legal proceedings if Scottish ministers allow him to return home to Tripoli.

The man convicted of the Lockerbie bombing has signed a secret document agreeing to drop legal proceedings if Scottish ministers allow him to return home to Tripoli.

Abdelbaset Ali Mohmed al Megrahi, who is appealing his conviction, has given the document to the Libyan government on the instruction that they cannot hand it over until Scottish ministers agree to his transfer.

His decision has led to an international political impasse as Kenny MacAskill, the Justice Secretary, cannot complete the transfer until Megrahi has dropped the appeal. Supporters are pushing for the "compassionate release" of Megrahi as a preferable alternative.

Legal experts say the minister could agree to such a move without an application from the Libyan, who is suffering terminal prostate cancer and whose condition has deteriorated.

There is confusion about how the prisoner transfer agreement works. One legal expert said that ministers have to give Megrahi a decision "in principle" before he drops proceedings, but officials say that is not the case.

Colonel Muammar Gaddafi urged Gordon Brown to allow the repatriation of Megrahi at the G8 summit in Italy. The UK and Libyan governments signed a prisoner transfer agreement earlier this year, and Mr MacAskill is consulting all of the parties concerned before making a decision.