A new campaign for compassionate release of the man convicted of the Lockerbie bombing comes with a claim of police interference at the start of the investigation.

As the Justice For Megrahi campaign was launched yesterday, Father Patrick Keegan, the priest in Lockerbie at the time, revealed that he had been visited by police during the inquiry and asked to keep to the official line - that Libya was responsible.

Fr Keegan and Dr Jim Swire, whose daughter Flora died in the tragedy that killed 270 people on December 21, 1988, yesterday launched the campaign calling for the people of Scotland to show compassion towards the man convicted of the bombing and allow his release on bail.

Speaking yesterday to launch the campaign, they revealed that they will be writing to MSPs and heads of all religious groups to garner support.

The launch comes just days after The Herald published the first interview with the wife and family of Abdelbaset Ali Mohmed al Megrahi, the Libyan serving a life sentence in HMP Greenock for the bombing.

Speaking exclusively to this newspaper, Aisha Megrahi said: "Please release him so he can spend what few days he has left at home with his family."

Just two weeks before the 20th anniversary of the UK's deadliest terrorist attack, she described her heartbreak at discovering that her husband is suffering from terminal cancer and of being able to see him for only 30 minutes a week, in line with prison rules.

Last month, appeal court judges ruled that Megrahi should not be let out on bail while his lengthy appeal continues, provoking fears that he will die in jail before his case can be heard. Lawyers are now expected to apply to Scottish ministers to seek his release from prison on compassionate grounds.

The campaign team, which includes Professor Robert Black, one of the architects of the original trial at Camp Zeist, hopes to influence public opinion to aid such a move.

Fr Keegan, who witnessed the aftermath of the bombing, spoke yesterday of his conviction that Megrahi is innocent and said he was moved to speak out after reading of the family's suffering in The Herald.

"My conscience has moved so much over the past two days that I wrote to Mr Megrahi offering him my support, telling him that I was convinced he is innocent and that I would willingly offer support to him and his family," said the priest.

"I can only imagine what his wife and family go through when visiting him for just half an hour a week and the constant wondering whether when they say goodbye - whether it will be the last.

"I really became convinced of his innocence when the whole thrust of the case shifted from Syria and Iran to Libya alone. Interference in my own life by the investigation team convinced me.

"A police officer asked to come along and speak to me. I listened to him for quite a while and then I said: Have you come here to ask me to be silent?' He said that the point was that when you speak people listen and we would appreciate it if you could follow our line of Libya alone'.

"I complained to the Lord Advocate about it at the time and got a very bland response. The very fact that they interfered and took the trouble to come to talk to me made up my mind that I was on the right track. Other people had similar experiences."

Dr Swire, who yesterday visited Megrahi in prison for the second time, said he noticed a change in the Libyan's appearance.

"As a doctor I am certain that if he were out and with his family rather than in custody, then he would be able to live much longer," he said. "He is clearly a man who is not physically well."

He paid tribute to Megrahi's family for their loyalty, which had extended to the Libyan's daughter Ghada deciding to get married in Barlinnie prison when her father was held there.

A spokesman for the Crown Office said: "While the appeal is ongoing all that is appropriate for us to do is comment in court on the evidence."

The campaign group plan to mark the 20th anniversary of the disaster later this month with a service in the chapel of Heathrow Airport.