Lucy Adams and Carolyn Churchill Labour has been plunged into a row over the party's criticism of the Scottish Justice Secretary's visit to the man convicted of the Lockerbie bombing.

Opposition politicians rounded on Kenny MacAskill after he met Abdelbaset Ali Mohmed al Megrahi as he considers a request for him to be transferred to Libya. Labour's justice spokesman, Richard Baker, accused Mr MacAskill of setting a "dangerous precedent" by visiting the Libyan in Greenock Prison, where he is serving a 27-year sentence.

He said: "Does every convicted murderer get a chance to meet the Justice Minister if they fall ill? Megrahi's appeal is ongoing and Mr MacAskill should not be meeting this man."

But Tam Dalyell, the former Labour MP who has long argued Megrahi's innocence, told The Herald: "I feel very strongly that Mr MacAskill was right to have gone to see Mr Megrahi.

"He was my opponent and I have disagreed with Mr MacAskill on many matters, but on this, I strongly support him."

When asked if criticism of his visit was wrong, he replied "totally" before adding of the Justice Secretary's decision: "He has already seen the relatives of victims of the bombing. He has already seen the US law officers and frankly it's a unique case.

"I believe Megrahi had nothing to do with the crime and that he was a sanctions-buster for Libyan airlines.

"But on this particular point, I think it's totally unfair to criticise Mr MacAskill for going to see him. I wish Labour members of the Scottish Parliament had shown more interest in the whole Lockerbie saga and clearly Mr Baker knows little about it."

Megrahi, 57, who was convicted of the bombing of Pan Am flight 103 in December 1988, which left 270 people dead, has terminal prostate cancer and is not expected to survive to see the culmination of his appeal.

In May the Libyan Government applied for the prisoner transfer of Megrahi under a controversial agreement signed with Westminster. However, for the transfer to go ahead Megrahi would have to first drop his appeal.

Last month The Herald revealed that Megrahi had applied to return to Tripoli on "compassionate release" because he is terminally ill.

Technically he could continue his appeal, but there is a growing expectation that he would be encouraged to first drop legal proceedings.

Mr MacAskill, who has the final say over whether Megrahi should be transferred or released, arrived at HMP Greenock at 9am and left an hour later, making no comment. Megrahi's lawyer Tony Kelly also took part in the visit.

Professor Robert Black, one of the architects of the trial at Zeist, said the visit was a "first" in Scottish legal history, but expressed concerns about any pressure being placed on Megrahi to drop the appeal.

A Scottish Government spokesman said: "The Justice Secretary is quite clear that he must have the fullest picture possible before making this important decision.

"To suggest he may do the same for any other convicted prisoner is just ridiculous. This is a unique situation."