A judge has ruled that a severely disabled teenager should stay with her foster family of 11 years, despite a plea by the girl's birth mother to have her back.

Lord Philip said that the birth mother, a 35-year-old college lecturer, did not fully appreciate the "demanding and unrelenting" task of caring full-time for her 17-year-old daughter who suffers from Angelman's syndrome, says a report in the Glasgow Herald this week.

But the loving care of the girl's foster family had enabled the teenager, who has a severe learning disability, her to flourish beyond all expectations.

She was taken into care after her birth mother who was 18 when her daughter was born, found it impossible to cope on her own.

Since she was six, the girl has been in the foster care of a 55-year-old woman from Fife. She and her husband have four children of their own and foster two other children, who are both autistic.

The foster carers thought the girl's placement would be permanent and would continue when she was adult but her birth mother maintained that it had always been intended that she would get her daughter back when she became able to care for her.

Lord Philip acknowledged that the mother, who has now remarried and lives in Glasgow, was devoted to her daughter and had maintained contact with her but said it was "vital" that she should feel secure in familiar surroundings with as little interruption to her routine as possible, said the Herald report.

He praised the foster mother and family's care as "exceptional".