UK Foreign Secretary William Hague has said a TV appearance by the Lockerbie bomber will intensify the “anger and outrage” at his release from jail.
Abdelbaset al-Megrahi was at a rally broadcast by Libyan state television.
Mr Hague said it was “a further reminder that a great mistake was made” when he was freed by the Scottish government nearly two years ago.
Scots Justice Secretary Kenny MacAskill said all the rules on compassionate release had been followed.
Mr Hague said the medical advice on which the decision had been made now appeared to be “pretty much worthless”.
However, Mr MacAskill said it was the best information available at the time.
“The medical evidence was provided by the director of health and public care at the Scottish Prison Service,” he said.
“He’s the most senior doctor that we have there and, as I say, this is an inexact science.