A health trust today promised an inquiry into its treatment of a mentally ill woman who was killed by her father to end her suffering.

James Lawson, 52, of Georgia Avenue, Worthing, helped his daughter, Sarah, 22, take a drugs overdose.

When that failed to kill her he placed a plastic bag over her head, then used a pillow over her face and his hand to suffocate her.

The roof tiler denied murder but changed his plea yesterday before a trial at Maidstone Crown Court, Kent, to admit manslaughter on the grounds of diminished responsibility.

Worthing Priority Care NHS Trust, which runs Homefields psychiatric hospital - from which Miss Lawson was discharged hours before her death - said it was setting up a review of the case.

It released a statement saying: "We deeply regret the tragic death of Sarah Lawson.

"The trust will immediately set up a review, with an independent chairman, into Miss Lawson's care and treatment. Its findings will be made public."

The court at Lawson's trial heard that his daughter had suffered from manic depression for more than ten years and had a long history of self-harm and suicide attempts, which had started through an obsession with guitarist Richie Edwards of the pop band Manic Street Preachers.

The guitarist was known to have harmed himself, and is believed to have committed suicide by throwing himself from a bridge.

Lawson told police he had taken part in the mercy killing in April last year as his family could take no more. He felt the NHS had repeatedly failed to help his daughter.

The family wanted the 22-year-old admitted to a secure psychiatric unit to stop her hurting herself.

Miss Lawson was taken into Homefields the day before she died. But she was ejected the next day for allegedly smoking cannabis.

The court heard that six hours after leaving the hospital the father helped his daughter to die.

Miss Lawson's mother has called for better care facilities for mentally ill patients to prevent other families going through their torment.

Karen Lawson, also of Worthing, is separated from her husband but has said she supports his helping their daughter to die to end her suffering.

After yesterday's court hearing she said: "I want to appeal to those who are in a position of power to investigate the level of care mentally ill patients receive.

"Don't let there be another Sarah and another family traumatised by watching their child deteriorate before their eyes ... surely society cannot allow this to go on."