Hundreds of crucial files relating to the contaminated blood scandal went missing after being removed by government officials, sparking fears of a cover-up.

Around 950 files relating to blood policy were “checked out” by staff going back years, a Government Internal Audit Agency investigation discovered last year.

The report has been released under Freedom of Information laws to campaigner Jason Evans, whose father died in 1993 having contracted hepatitis and HIV.

The 29-year-old, who is suing the government for negligence, claims the removal of documents “probably goes back decades” and could form part of a government cover-up.

He told HuffPost UK: “While looking into this issue, I came across the odd file which had been misplaced while on loan to a government department – which turned out to be the Department of Health – but these seemed like one-offs and I never imagined the scale of it.

“Each one of these files contains anywhere between 100 and 300 documents which means that tens of thousands, perhaps hundreds of thousands of documents went missing.

“This raises real questions about a cover-up and this has been kept under wraps for decades.”

Evans, who runs the campaign group Factor 8, also revealed he was initially denied access to the report under Freedom of Information, but finally managed to obtain the information.

He said: “It is extremely frustrating dealing with the Department of Health for anything. From when I first asked for the report, it took four months before I got it and there was so much wrangling.

“Initially, they said they did not want to give it to me because it was ‘not in the public interest’.”

Evans says these new findings mean previous enquiries into the scandal would not have had access to all the information.

“So many people who campaigned about this scandal for decades were told by three different health ministers that all the documents were either in the public domain or destroyed” he told HuffPost UK.

“They died thinking this was the truth – but it was not.

“I feel extremely sad on behalf of my dad and the hundreds of others who have died and the entire community affected by this scandal.”

The contaminated blood scandal has been labelled the worst treatment disaster in the history of the NHS.

Thousands of patients were infected with HIV and hepatitis C via contaminated blood products in the 1970s and 1980s.

Many had haemophilia, a blood-clotting disorder, and relied on regular injections of clotting agent Factor VIII, which was made from pooling human blood plasma.

Britain was running low on supplies of Factor VIII so imported products from the US, where prison inmates and others were paid cash for giving blood.

Evans’ solicitor Des Collins, senior partner at Collins Solicitors which is representing more than 1,000 victims, their families and seven campaign groups, said: “The sad fact is that despite 1,000 crucial files going ‘missing’, there is very little that will surprise me in relation to the facts in this important inquiry.

“We know that there has been a government cover-up.

“We now have clear evidence that vast numbers of documents were removed and not returned.

“We need to get to the bottom of why this happened, exactly what was in the files and what the people who in effect ‘made them disappear’ were trying to hide.”

In September, the first UK-wide probe – the infected blood inquiry – heard that more than 25,000 people could have been affected.

The report released to Evans and dated November 6 2018, said almost 1,000 files relating to blood policy had been checked out by officials.

These included around 450 files checked out by Department of Health and Social Care staff and a further 500 by Department for Education staff.

The report said that while the DfE has been co-operating with recovering the files, 45 files remain unaccounted for.

A spokesman for the Department of Health said: “We are committed to being open and transparent with the Inquiry and have waived the usual legal privileges to assist the process.

“We have already sent thousands of documents to the inquiry, and will continue to send more when necessary.

“The inquiry has always been free to request any files they wish to review and we will ensure these are shared as soon as possible.”

In September, the inquiry heard emotional testimonies from people infected with HIV and hepatitis.

Eleanor Gray QC, acting for the Department of Health and Social Care, told the inquiry that the treatment of information surrounding contaminated blood products has been “at worst, a cover-up, at best a lack of candour about past events”.

The inquiry has heard how some patients said their medical records disappeared or were doctored.

Former health secretary Lord Owen has said there was a “cover-up” and “incriminating evidence” had been suppressed by the Government to prevent victims taking legal action.