British officials have admitted a "serious error of judgement" after a disturbed teenager was placed with a foster family and sexually abused their children.

Social workers failed to tell them the teen — who cannot be named for legal reasons — had a history of sexual behavior involving youngsters.

He then went on to attack their two young children, and was jailed at Cardiff Crown Court after admitting rape and sexual assault.

Judge Nicholas Cooke QC said the case was a tragedy for the couple, whose only wish was to serve the community by helping the teenager.

Vale of Glamorgan council has launched an investigation into the case, and said it deeply regrets the distress and harm caused to the family.

"Although the inquiry is still at an early stage, it has become clear that there was a serious error of judgement in placing the young man in this family," Phil Evans, Director of Social Services, added. "Staff are taking this matter very seriously. We're doing all that we can to find out what went wrong and to ensure that such events are never repeated."

Allegations about the teenager's sexual behavior were first made in 2004, when it was claimed he acted in a sexually inappropriate way toward another boy.

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