Tommy Sheridan, who is expected to be released under licence on Monday on the Home Detention Curfew programme a year after his conviction on perjury charges, is understood to have been banned from public speaking as part of his licence.

Such a condition has not been imposed on a prisoner in Scotland before.

The ban is understood to impose a condition of silence on Sheridan for a period of six months. The Sheridan family's counsel, Advocate Paul McBride QC, said the condition risked breach of the European Convention of Human Rights.

“There’s a human rights issues, as I’ve never heard of someone being released and told don’t speak in public. It sets a very dangerous precedent,” he said.

“It’s not appropriate to a democratic society because if someone is released they are either part of society or they are not. If they are not fit to be released, then they should finish their sentence. There are rapists and murderers who have not had this condition imposed.

“Although Tommy’s unable to campaign for public office because of his conviction, it seems odd that there are restrictions being imposed about what sort of work he can do, particularly in the current economic climate.

“It’s an utterly ineffective and inefficient thing to do, as there’s nothing to prevent others speaking on his behalf. It’s silly and unnecessary, and probably challengeable in the courts,”

The Scottish Prison Service said in a statement : “Conditions are associated with home detention curfews, but these conditions are not universal and they do pertain to individuals.”