A hospital trust is facing legal action by relatives of a woman who died after she was given the wrong dose of a drug.

Brighton and Sussex University Hospitals Trust has admitted failures in its treatment of Margaret Pye who died aged 72 on May 3 last year.

The trust, which is already facing allegations of poor care of the elderly at one of its hospitals following a BBC documentary, has apologised to the patient's family after an inquest highlighted complete failures by doctors during Mrs Pye's treatment at the Princess Royal Hospital in Haywards Heath.

Now Mrs Pye's family say they have been forced to take legal action because of what they say is the appalling way their complaints about their late mother have been handled.

Mrs Pye's daughters Sarah Beck, 49, and Caroline Warburton, 53, are furious that communications broke down from the day their mother was admitted to the Princess Royal, when they expressed concerns about their mother's care, right up to today.

They say the family has continued to be be excluded from the trust's inquiry into the failures and that their letters of complaint or requests for information have gone unanswered.

The trust did write to the two sisters in August last year when a spokeswoman apologised for what it admitted were short comings and failures to meet its standard of care.

In November 2004, six months after Mrs Pye's death, the sisters wrote an extensive letter to the trust and say no reply was ever received.

The family wrote again in March this year asking why they had not received a response.

The letter said: "How can I or the rest of my family move on whilst this is still hanging over us?

"Has your trust learned nothing at all from the comments made by the coroner's inquest last July?"

The family have instructed a solicitor to take up their case and the Brighton and Hove Unwaged, Advice and Rights Centre will also represent them.

Mrs Pye, a grandmother, died after she was administered an incorrect dose of the highly toxic drug Lithium, a mood stabiliser which is used to treat bipolar disorders.

An inquest was held into Mrs Pye's death in Brighton in July 2004 when the verdict decided that: "Mrs Pye died on May 3 2004 during essential treatment to correct lithium toxicity where there had been a complete failure by the hospital's doctors in whose care she had been, to address and treat that toxicity as soon as it was discovered on April 21 2004."

Mrs Pye's husband of more than 50 years, Philip, died less than a month after losing his wife. The couple had barely spent a night apart during their marriage.

They had lived in the same house in Haywards Heath for 35 years until Mr Pye was diagnosed with terminal cancer early in 2004.

He was admitted to a hospice in Wivelsfield but after a week, it became clear Mrs Pye could not be left alone at their home.

She fell several times, suffered from diabetes, arthritis, high blood pressure, eye problems and long term depression.

Mrs Pye was taking lithium for a bi-polar condition and was taking 15 medications a day as well as two insulin injections and it was felt she would be safer in a nursing environment.

She was moved into the Princess Royal Hospital in Haywards Heath on April 16 2004 and soon became confused.

Her family say they expressed concern to nursing staff and questioned her care and that perhaps her medication had been changed.

Mrs Pye's daughter Miss Beck, a former hospital care worker, of Barnett Road, Brighton, said: "She was going downhill and it was like she was being doped. She was talking as if she had had a stroke. They kept saying nothing had been changed."

Days after being discharged from hospital, Mrs Pye's condition worsened and she was admitted to the Brighton General Hospital.

She was transferred from there to the Royal Sussex County Hospital in Brighton because it was discovered she had been receiving a dosage of lithium higher in hospital than she was getting at home and the levels had poisoned her.

Mrs Pye underwent dialysis to help deal with the toxic affects of the drug but died on May 3 2004, just six days after leaving the Princess Royal.

Mrs Pye's family wants the trust to be held responsible for the poor level of care. Miss Beck said: "They caused her death and they caused unbelievable mental trauma for my family."

A spokesman for the trust said: "We take all complaints very seriously. If we have received the letter we will consider and address all the issues and respond in due course."