It would be an abominable cruelty to let this man die in prison,' Swire told the BBC.

But US relatives reacted differently.

Susan Cohen, whose daughter was a victim, said the suggestion that Megrahi should be freed on compassionate grounds was 'vile'.

Speaking to BBC radio from her home in New Jersey, Cohen said: 'Any letting out of Megrahi would be a disgrace. It makes me sick, and if there is a compassionate release then I think that is vile,' she said.

Cohen said the British government would be betraying the Lockerbie victims if it decided to free al-Megrahi, who was convicted at a trial held in the Netherlands in 2001 heard under Scottish law. The judges ruled that he should serve a minimum of 27 years in jail.

'We were told he would stay in prison, so the British government should be ashamed of itself,' she said.

Al-Megrahi has always protested his innocence and launched a fresh appeal against his sentence earlier this year. A United Nations observer and Scotland's Criminal Case Review Commission have said they have 'grave concerns' that the Libyan could have been a victim of a miscarriage of justice.

If al-Megrahi should be released on compassionate grounds and transferred to Libya, his appeal would be upheld.