Former Scottish First Minister Henry McLeish has described comments by the FBI chief on the Lockerbie bomber's release as "totally out of order".
Scottish Justice Secretary Kenny MacAskill freed terminally ill Abdelbaset Ali al-Megrahi on compassionate grounds on Thursday.
FBI director Robert Mueller said the decision gave "comfort to terrorists".
Mr McLeish said it was an unfair slur on the Scots justice system. A former lord advocate said it was "appalling".
Megrahi, who has always claimed his innocence, served seven years, five months and four days of his life sentence for the bombing of the Pan Am jet over Lockerbie in 1988, in which 270 people died.
Since the 57-year-old's release, Mr MacAskill has been criticised for his decision, particularly from relatives of Americans killed in the bombing.
Mr Mueller, who was the US Assistant Attorney General responsible for the Lockerbie investigation, said he was outraged by the release, which he said made a mockery of the grief of the victims' families and undermined the rule of law.
In a letter to the justice secretary, he wrote: "Your action in releasing Megrahi is as inexplicable as it is detrimental to the cause of justice. Indeed your action makes a mockery of the rule of law.
Megrahi returned home to Libya after his release
"Your action gives comfort to terrorists around the world who now believe that regardless of the quality of the investigation, the conviction by jury after the defendant is given all due process, and sentence appropriate to the crime, the terrorist will be freed by one man's exercise of 'compassion'.
"Your action rewards a terrorist even though he never admitted to his role in this act of mass murder and even though neither he nor the government of Libya ever disclosed the names and roles of others who were responsible."
However, Henry McLeish said Mr Mueller's intervention was "totally out of order".
"Let's as Scots, despite the adversity, be conscious that it is Scotland and our criminal justice system which holds its head high throughout the world," he told BBC Radio Scotland.
"It doesn't help if some ill-informed remarks are made by the director of the FBI towards that when it's, quite frankly, none of his business.
"It would be the equivalent of the Metropolitan Police chief writing to Barack Obama to complain about a decision that has been made.
"He has a view - fine - but that was a slur on the Scottish justice system that we didn't deserve as part of the wider debate."
Henry McLeish said the US had a punitive criminal justice system
He said there was a different culture in the United States which "did not see any scope for compassion" in its criminal justice system.
Lord Fraser of Carmyllie QC, the former chief prosecutor who launched the case against the Lockerbie bomber, also hit back at Mr Mueller's attack.
He told The Courier newspaper: "As a former lord advocate I'm quite appalled that the head of the FBI, Robert Mueller, should have set his face so openly against Scotland.
"When he drives in to work he listens to pipe music and it shocks me that he has become so disillusioned with us that he now rejects us as pro-terrorist.
"We are not and he knows that from his regular visits to Edinburgh."
Prime Minister Gordon Brown's spokesman also dismissed the claims, saying: "I don't see how anyone can argue this has has given succour to terrorists."
The SNP's Michael Matheson said: "Scots across the country know that Mr Mueller's comments were an entirely inappropriate attack on our justice system.
"This decision was made in the right way for the right reasons and has upheld the principles of our legal system."
Meanwhile, the Catholic Church in Scotland has voiced its support for Mr MacAskill's decision.
The Archbishop of Glasgow, Mario Conti, said: "I personally, and many others in the Catholic community, admired the decision to release Abdelbaset Ali al-Megrahi on grounds of compassion which is, after all, one of the principles inscribed on the mace of the Scottish Parliament by which Scotland's government should operate.
"The showing of mercy in any situation is not a sign of weakness.
"Indeed in this situation, with the pressures and circumstances of the case, it seemed to me a sign of manifest strength.
"Despite contrary voices I believe it is a decision which will be a source of satisfaction for many Scots and one which will be respected in the international community."
Rev Ian Galloway, the Church of Scotland's church and society convener, said in a message to MSPs: "The apparent celebrations in Libya following Megrahi's release on compassion grounds must have stuck in the throat of many, especially the relatives of the victims."
He said it was an inappropriate response to a difficult choice.
"Yet despite those pictures of flag-waving and cheering crowds, the Church of Scotland believes that the decision to release Abdelbaset Ali al-Megrahi on compassionate grounds was the right one," he added.
"This decision was not simply about the fate of one man. Nor was it about the reaction of his fellow countrymen or the politics of the relationships between nations.
"It was about what it is to believe in justice, what it is to believe in mercy, what it is to be truly human."