Many people have died from contaminated blood
An independent public inquiry into the supply of contaminated NHS blood to haemophilia patients is set to hear evidence from those affected.
During the 1970s and early 1980s, nearly 5,000 people were exposed to hepatitis C and of these more than 1,200 were also infected with HIV.
More than 1,700 patients have since died, and many more are terminally ill.
The inquiry is being funded privately, and not by the government who said treatments were given in "good faith".
Labour peer Lord Archer of Sandwell, a former solicitor general, is leading the inquiry which is due to report in late summer.
In his opening statement, Lord Archer said the inquiry would investigate the circumstances surrounding the supply of contaminated NHS blood and blood products and make recommendations to assess the needs of patients and bereaved families.
BBC's Newsnight programme has reported seeing documents suggesting experts were aware of the threat at an early stage, but transfusions were not stopped.
Lord Archer said the first purpose of the inquiry was to find out why and how this contamination occurred to help those affected come to terms with what had happened.
He added: "Hopefully, we may discover something that will help for the future and we can learn some lessons."
Lord Archer said the Department of Health had told him it would help as far as it could and he promised to ask officials for documents that could be relevant.
Any evidence "of anything which is blameworthy" would be investigated, he added.
Asked about the Newsnight allegations, Lord Archer said: "I cannot comment on what evidence we are going to have, because we have not heard any evidence."
He said if allegations were made against particular doctors or consultants they would be asked to the inquiry.
Former health ministers had also offered to help the inquiry, Lord Archer added.
Meanwhile former health minister Lord Owen said he had secured extra money in 1975 to help avoid using blood donations from abroad, but had later found out it had not been spent.
Lord Owen said: "If we had gone in for self-sufficiency, I am pretty confident we would have had a substantial reduction in contaminated blood supplies.
"It would not have completely ruled it out, but I think much fewer people would have got Hepatitis C and fewer people would have got Aids."
Haemophilia is a rare inherited bleeding disorder in which blood does not clot normally.
The main problem is internal bleeding into joints, muscles and soft tissues.
Currently, the condition can only be treated by injections of the clotting chemical, known as factor VIII.
In the early 1970s, patients were treated with blood proteins that came in dry powder form and could then be reconstituted with water - plasma from 10,000 donors went into the product.
The treatment, which often came from patients in the United States who were paid for giving blood, exposed 4,670 patients to hepatitis C infection.
In 1981 it was also found that some plasma products were infected with HIV.
After the mid-1980s the plasma products were treated with heat to kill viruses.
Successive governments have refused to admit any fault but payments of varying amounts have been made to people who caught HIV.
In 2004, the Skipton Fund was set up for those infected with hepatitis C virus but no payments were made to those who died before 2003.
Roddy Morrison, chairman of the Haemophilia Society said he was absolutely delighted the inquiry was going ahead.
"It's taken 19 years of campaigning.
"There's never been a chance for people to tell their stories and to know that people with the right skills will be able to look at this and establish what happened and could things have been done to prevent this.
"There's a huge number of questions that need to be answered."
A spokesperson for the Department of Health said they had been open and transparent about the issue.
"We have great sympathy for those who were infected with Hepatitis C and HIV and understand why they want to know how it happened and why it could not have been prevented.
"However, the government of the day acted in good faith, relying on the information available at the time."
Professor Christine Lee, emeritus professor of haemophilia in the University of London agreed there was a lot of misunderstanding about what was known at the time.
"The hepatitis C virus wasn't isolated until 1989 and there wasn't a blood test until 1991.
"Also there was no alternative and the life expectancy of someone with haemophilia was 20 years," she said.
But she added that the inquiry may give patients the chance to vent their feelings and get some closure.