A grieving mother claims a review into the circumstances surrounding her daughter's death is a whitewash.

Karen Lawson was speaking 17 months after Sarah Lawson, 22, was killed by her father James in what was described in court as a mercy killing.

Ms Lawson has refused to take part in an investigation by health bosses because she does not think it will be independent.

She says it will not reveal where the system failed her daughter, who died within hours of being released from Homefield Psychiatric Hospital, run by Worthing Priority Care NHS Trust.

Ms Lawson said: "It is an insult for the NHS to be investigating the NHS. All the review panel are in some way involved with the trust.

"My daughter is dead and all they will do is ask cosy questions at their review. They must answer for their actions. I feel terribly let down and want nothing to do with it."

Sarah was killed by her 53-year-old father, who helped her to die through a cocktail of drugs and suffocation by a pillow on April 22 last year. He walked free from court last June after a judge accepted he had killed his severely depressed daughter in an act of mercy.

Ms Lawson, 46, said: "My husband had to go to court to answer for his actions. The trust should also be held accountable as it failed our daughter."

Ms Lawson, who lives in Worthing and is now separated from her husband, said: "It is clearly a whitewash. Not one member of that panel could be deemed independent. But when I offer to help I am ignored. I have no faith in the process."

Sarah, who had a history of depression, was first seen by the trust in 1997.

Ms Lawson has submitted questions to the panel, which met for the first time last month, about the standard of service Sarah received.

A health authority spokeswoman said the aim of the review was to establish the facts and that all panel members were independent of the review's commissioning agencies.

She said: "The review process will provide the opportunity to clarify the circumstances and events leading up to Sarah's tragic death and make recommendations which will be used positively to inform future practice in mental health services.

"Due to the complexity of the process and the need to involve everyone responsible for Sarah's care, the review would normally be expected to take up to six months to complete."

The findings of the review will be made public.