Families who fear their loved ones were killed by senior nurse Ann Grigg-Booth are demanding a public inquiry into the circumstances around her arrest.

The nurse, who was facing trial for the murder of three patients, was found dead at her home in Nelson on Monday.

Solicitors representing six of the relatives of the alleged victims said a letter seeking a public inquiry had been despatched to Health Secretary Patricia Hewitt, right, today.

And the lawyers revealed they had a statement from a client in which Grigg-Booth was accused of administering an extra amount of powerful pain-killer to a patient who was on a self-dosing programme.

The patient could administer the pain killer herself, up to a limit, and no more should have been allowed unless on the approval of a consultant.

Simon McKay, of McKay Law, of Leeds, said: "Grigg-Booth produced a syringe at midnight and administered a very large dose into the patient's leg."

Grigg-Booth, a former nurse at Airedale General Hospital, Steeton was also to face trial in April accused of the attempted murder of a middle-aged man and 13 counts of unlawfully administering poison to 12 others.

The police investigation focused on the injection of painkilling opiates, including diamorphine, to patients between 2000 to 2002.

Relatives want the Health Secretary to agree to a public inquiry, despite the promise of an independent probe by the West Yorkshire Strategic Health Authority (WYSHA).

The Health Secretary has the power to order a public inquiry under the 1977 National Health Act. Mr McKay said only a public inquiry would satisfy the public interest and the victims' relatives.

It was important that the inquiry led to lessons being learned from lapses which must have existed, he said.

Unlike an independent inquiry, a public inquiry could lead to a recommendation for criminal prosecution, said Mr McKay.

He said at an independent inquiry, there was no right of representation for relatives or for funding for them to attend.

A public inquiry could also make recommendations for reform and change, while the recommendations of an independent inquiry need not be carried out, he added.

Mr McKay said his firm had originally written to the Department of Health in March this year making a similar request.

But they were told that they would have to await the outcome of the criminal proceedings.

Circumstances had now changed with Grigg-Booth's death and they had immediately made a further request.

Mr McKay's colleague, Rick Armstrong, said the inquiry should focus on the system used by the hospital of administering drugs and who had authority to administer them.

Questions such as what the hospital was doing and what the consultants were doing to allow it to happen should be asked.

A Nursing and Midwifery Council spokesman said nurses were increasingly qualified to prescribe drugs - about 40,000 so far out of a total nurse population of 600,000. Strict rules surround the administering of Class A drugs.

The independent inquiry will be led by a top lawyer, probably a QC, and will consider circumstances surrounding the alleged attempted murder of a 42-year-old man and the 13 charges of administering noxious substances.

Airedale NHS Trust is also conducting its own internal inquiry.