The Court of Session in Edinburgh ruled that Scottish ministers were in contempt of court because they had failed to enforce an order preventing warders from opening letters sent to the murderer.

Beggs, 41, was convicted of murdering Barry Wallace, 18, from Kilmarnock. The teenager was on his way home from a Tesco’s Christmas party in 1999 when he was picked up by Beggs. He took him back to his flat where he sexually assaulted and murdered him, before chopping him up and dumping his limbs and torso in Loch Lomond and his head in the sea off the Ayrshire coast. He fled abroad but later surrendered to police in Amsterdam.

He has so far served three years of a life sentence and must serve a minimum of 20 years before he can be considered for parole.

Last year Beggs launched an appeal against his conviction, claiming that under human rights laws a fair trial was impossible because of the publicity surrounding his case.

He also complained that his post was read by staff at Peterhead Prison and ministers gave an undertaking that his legal letters would not be opened. But Beggs claimed that “privileged correspondence” from legal advisers had been interfered with last year.

A Scottish Executive spokesman confirmed that Beggs’s mail had been opened, but said ministers were seeking leave to appeal the contempt ruling and “therefore, it would be inappropriate to comment further”.

A Scottish Prison Service spokesman said ministers accepted there was a breach of the undertaking given to the court, but it had been “inadvertent”.

However Scotland’s senior judge, the Lord President, Lord Cullen, ruled that the undertaking not to interfere with Beggs’s correspondence had “not been taken seriously enough”. No penalty was imposed on the Executive.

Beggs was convicted in 1987 on two charges of unlawful wounding, was also found guilty of a murder before the conviction was overturned on appeal. In 1991 he was jailed for six years for a razor attack on a man he had met at a gay disco and taken back to his flat.

Explore UK News

• Crime News

• Education News

• Health News

• Science News

• Scotland News

Times Recommends

• DIY video helps the WI get to grips with sex
• Artists urge nation to save Titians
• Go home, Iraqi leader tells Britain