A coroner has criticised a hospital where an elderly patient died after accidentally being given a massive overdose of a painkiller.

Instead of being given 2.5mg of diamorphine, Iris Baxter, 86, was injected with 10mg after a mistake by nurses who read the wrong part of her medical charts at Brighton General Hospital.

An inquest heard Mrs Baxter, who lived at the Arundel Park Lodge nursing home in Brighton, was dying at the time of the overdose and it was not believed the drug directly caused her death.

Brighton and Hove Coroner Veronica Hamilton-Deeley, who recorded a verdict of death by natural causes, told the hearing she intended to write to the hospital voicing her concerns.

An investigation by detectives revealed the overdose was an innocent mistake and there was no crime involved.

The coroner said: "One of the things this inquest has highlighted is that medical charts should not be treated like somebody's shopping list. They should be treated with proper respect, they should be signed, timed and they should be legible."

Doctors and nurses who were working on E3 ward on the day of the incident in August gave evidence at the hearing.

Mrs Baxter suffered from dementia and depression and was still grieving for her husband, who died in 1996.

Her health deteriorated after she fell and fractured her shoulder. She was admitted to the hospital as an emergency and suffered a cardiac arrest.

She was successfully resuscitated but never regained consciousness.

After discussing her condition, her family and medical staff agreed she should not be given any more treatment but kept free from pain and comfortable until her death, which was expected at any time.

She appeared to be suffering some pain and a doctor prescribed a morphine pump, which was supposed to give her diamorphine and two other drugs.

But there was a delay on the ward and it was not until hours later that nurses started to try to find the drugs for the pump.

There were further delays because nurses queried the doctor's prescription and one of the drugs was not available at the hospital and had to be delivered by taxi from the Royal Sussex County Hospital.

Meanwhile, two nurses were told to administer diamorphine by injection because Mrs Baxter was showing signs of being in pain.

But instead of giving her the right dose of 2.5mg they gave her the 10mg dosage prescribed for the pump, which was due to be administered over 24 hours.

She died five hours later. A post-mortem examination showed Mrs Baxter died of respiratory failure due to heart disease and bronchial pneumonia in association with the toxic level of diamorphine.

Her daughter Pamela Philpot, of Saltdean, told the inquest the family believed Mrs Baxter had momentarily died immediately after the injection was given but she started to breathe again.

An hour later, nursing staff realised a mistake had been made when a member of staff checked the charts and saw the wrong dose had been given.

Dr Alan Ireland, associate medical director of the Brighton Health Care NHS Trust, which runs the hospital, said the overdose was a serious incident and a review has been ordered of the hospital's system for prescribing drugs for the pump.