The child's adoptive parents, who cannot be named for legal reasons, claimed Essex County Council was negligent in not disclosing details of his "uncontrollable and vicious" character.

A High Court judgement on Wednesday ruled that Essex County Council was negligent in not passing on information to the parents about the behaviour of the boy.

The ruling is the first case of its kind and opens the way for the couple to seek substantial damages.

The decision is a complete vindication of their criticisms of the disorganised way in which Essex County Council went about this placement in 1995 Christopher Yemm, couple's solicitor

The child, who was five at the time of the adoption in 1996, was diagnosed as suffering from Attention Deficit Hyperactivity Disorder and has been under medication in special needs care since 1999.

The father told the court the adopted son's behaviour went "off the Richter scale".

The court heard that he threatened and attacked the adopted mother and, when she became pregnant, threatened to kill the unborn child.

Both parents said they were not properly informed of the boy's serious and emotional behavioural difficulties.

But the council denied any liability, arguing the parents were fully aware of what was known about the boy.

It said the boy had lived with the couple for a 14-month placement prior to the adoption in 1996 and this had given them time to see how he was settling in.

Council appealing

Essex County Council has been given leave to appeal.

A statement from the council said: "We are very disappointed by the judgement and very sad for all those involved."

However, the payout will be limited by the judge's decision that damages can only be awarded for the problems caused by the placement - and not for the later period.

The couple's solicitor Christopher Yemm said after the case: "My clients are delighted with this decision.

"The decision is a complete vindication of their criticisms of the disorganised way in which Essex County Council went about this placement in 1995."