Revealed: The British government was warned about the risks of infected blood in the 1970s

A commercial blood product at the center of the biggest treatment scandal in the history of the NHS was approved for use after government officials were told convicts were among the paid donors and that virus contamination “must be assumed”, company files show.

The product, given to haemophiliacs to help their blood clot, was injected into thousands of patients in Britain in the 1970s and 1980s, including young children, infected with AIDS and hepatitis C.

A single batch could contain plasma from 20,000 donors collected in US prisons and some of America’s poorest neighborhoods, where drug use and sexual infections were rife. One infected donation would contaminate the entire batch.

A enquiry led by Sir Brian Langstaff will report next month on the scandal, which has left around 3,000 people dead. He has already concluded that “mistakes have been made at individual, collective and systemic levels”.

The drug company Bayer provided 7,000 documents to the investigation, showing that its subsidiary, Cutter Laboratories, warned in licensing application documents in the 1970s that its commercial blood product Koate could contain viruses. It said: “Since the presence or absence of hepatitis virus in Koate concentrate cannot be proven with absolute certainty, the presence of such virus must be assumed.”

The product, known as a factor VIII concentrate, was approved in August 1976, along with similar treatments that provided a conduit for deadly viruses for years.

A government security committee was told that “US state prisons” were among the sources. Research has shown that there is a greater risk of hepatitis infection from prison blood and the Medicines Safety Committee was warned that the product “suffers because it is prepared from donations from multiple centres, which cannot be properly checked by inspection”.

Des Collins, of Collins Solicitors, who acted for 1,500 infected or affected people, said the licensing documents were “shocking” and products should not have been approved until viral inactivation was available. “There was a huge failure among ministers and successive governments,” he said.

Stuart Cantrill, 50, whose father Barrie died in 1989 after contracting Aids from a commercial blood product for haemophilia, said: “There were clearly some within the NHS and in government who were aware of the risks and chose to ignore them . They went ahead and used a product that would almost certainly infect everyone.”

Experts in the 1970s believed that the risk of a patient developing hepatitis B from the combined products outweighed the benefits of the treatment, but did not take into account the presence of deadlier viruses that had not yet been identified, particularly hepatitis C and HIV.

When cases of AIDS were first reported in the 1980s, officials and ministers failed to take action because of the risk of spreading the disease through the infected blood. The Observer flagged the risk in January 1983, warning: “A commercial blood product imported into Britain from the United States may pose a serious threat to the health of hemophiliacs.”

Four months later the Post on Sunday warned hospitals that use murderous blood. It warned that blood products collected from the US could be contaminated with HIV and “threaten the lives of thousands of Britons”.

It was an accurate and prescient warning, but the government said there was no conclusive evidence and failed to withdraw the contaminated product, infecting adult and pediatric patients with HIV. The dirty blood was administered for another two years before the heat treatment was introduced in 1985. Andy Evans, chairman of the Tainted Blood campaign, said it was “incredible” that the product was still licensed. “The evidence indicated that the treatment was dangerous and they did not take action,” he said.

Bayer said it voluntarily submitted documents to the investigation “to support the investigation’s understanding of historical events and actions of Bayer group companies.”

It said it was “truly sorry” for the tragic situation that had occurred and that therapies intended to save lives caused so much suffering.