Haemophiliacs who contracted HIV and hepatitis through contaminated blood products began giving evidence at an independent public inquiry yesterday.

Nearly 2000 patients who were exposed to HIV and/or hepatitis C from clotting agents such as Factor VIII have since died and many others are said to be terminally ill.

The inquiry in London - into what has been described as the worst treatment disaster in the history of the NHS - is being conducted by Labour peer Lord Archer of Sandwell, a former Solicitor General.

The hearings began in the wake of claims on the BBC's Newsnight programme on Tuesday that British doctors ignored warnings about using haemophiliacs to test out new blood products.

The inquiry's terms of reference are: "To investigate the circumstances surrounding the supply to patients of contaminated NHS blood and blood products; its consequences for the haemophilia community and others afflicted; and further steps to address both their problems and needs and those of bereaved families."

Lord Archer said: "Our purpose is to unravel the facts, so far as we are able, and to point to lessons that may be learnt."

Fellow Labour peer and fertility expert Lord Winston has described the affair as "the worst treatment disaster in the history of the NHS".

Haemophilia Society chairman Roddy Morrison said after the first day's hearings: "The evidence from today's sessions at the inquiry has been deeply moving as well as highly revealing of the plight of people exposed to blood-borne viruses through treatment with contaminated blood products by the NHS. It dramatically highlights why we have been campaigning for the last 19 years for their voices to be heard."

He said the "deeply shocking" allegations made on the Newsnight programme should also be investigated.

The programme claimed that, from the early 1970s to the mid-1980s, 4500 haemo-philiacs in the UK were exposed to lethal viruses through blood products designed to help them.

During the hearing Sue Threakall, whose husband Bob died in February 1991, aged 47, after contracting Aids following the use of clotting agent Factor VIII, said: "I shouldn't actually be here today. None of us should. Not the inquiry panel who are doing this unpaid, not the widows and certainly not most people sitting here today who are having to battle on a daily basis just to stay alive."

The reason for that, she said, was because the tragedy had been wholly avoidable, but warnings were ignored. And she added that the gross incompetence should have been acknowledged by the government of the time and dealt with honourably nearly a quarter of a century ago.

Newsnight disclosed that many haemophiliacs became infected from supplies of the clotting agent from abroad, and much of the plasma came from prison inmates in the US who were allowed to sell their blood even though there were questions about their health.

The programme said official documents had "mysteriously disappeared", although the government claimed some were shredded and others had not been released on grounds of commercial confidentiality.

Despite a warning from the head of Britain's public health surveillance centre, the Factor VIII imports were still used.