The mother of Sarah Lawson vowed to sue the health trust she claims failed her mentally-ill daughter, who finally begged her father to help her die.

Karen Lawson, 45, said her family was ignored as Sarah's mental state deteriorated and her suicide attempts became more regular.

Worthing Priority Care NHS Trust has promised to hold an independent review of its treatment of Sarah.

She died within hours of being released from Homefield Psychiatric Hospital, Worthing, which is run by the trust.

Karen was killed by her father James who helped her to die with a cocktail of drugs and suffocation with a pillow in an act of desperation to end her suffering.

In a statement a trust spokesman said: "We regret the tragic events that occurred in the hours following Sarah Lawson's discharge from Homefield on the evening of April 21, 2000.

"We are proposing there should be an independent review in which we would hope the family would want to participate."

The trust said Sarah, who had a history of drink problems, was known to mental health services in Worthing and had been offered a comprehensive treatment plan.

A spokesman said: "We did our utmost to engage with her and her family over a long period of time."

But Mrs Lawson claimed little was done to help her daughter.

And she said her and husband's efforts to get involved with her treatment were constantly thwarted. On the night before her daughter died, when the hospital asked Sarah to leave after allegedly giving cannabis to another patient, Mrs Lawson sat in an office for more than three hours trying to get the doctors to change their mind.

A trust spokesman said Sarah was a voluntary patient in Homefield Hospital and not detained under the Mental Health Act.

He said she was asked to leave after committing a major breach of an agreement about drugs and alcohol after being seen giving cannabis to another patient who was seriously mentally ill.

Mrs Lawson hopes her daughter's tragic death will force a change in mental health services so better facilities will be available for sufferers of depression.

Elaine Sola, director of Worthing Mind which deals with about 250 people a day suffering with severe mental health problems, said she was not surprised a carer had been pushed so far.

She said: "Carers are always frustrated because they are not given enough information or involved enough in treatment care plans.

"It is clear with Sarah there was obviously something wrong at an early age but it wasn't dealt with.

"We need to tackle problems early and get a proper assessment so people can be properly looked after."

Mind is currently working closely with Worthing Priority Care Trust to set up a crisis intervention centre, which would help people who were as desperate as Sarah.

The service, which has to be brought into force under the NHS plan by April 2004, would provide a team of doctors, nurses and psychiatrists to deal with a crisis as soon as it occurred.