Media playback is unsupported on your device Media caption Jason Evans father died of Aids after being infected with contaminated blood

Jason Evans was just four years old when his father Jonathan died after being infected with HIV through treatment with contaminated blood.

Now in what is understood to be the first case of its kind, Jason is taking legal action against the government for its role in his father's death.

More than 2,000 people - mostly haemophiliacs - have died after being infected with HIV and hepatitis C through blood treatments.

The victims were infected over 25 years ago, in what has been called the worst treatment disaster in the history of the NHS. But even now new cases are still being diagnosed.

BBC Panorama has spoken to Jason and some of the other families affected.

'The government knew it was dangerous'

Image caption Jason says patients would not have played Russian Roulette with their lives if they had known the risks

"My first memory of my dad is the last time I ever saw him," says Jason Evans. "It was my birthday, I was four years old."

Six weeks later, his father Jonathan died. He was 31 years old.

Jonathan Evans was one of many people to have been given a treatment known as Factor VIII.

Made in huge vats from the blood plasma of thousands of people it meant if just one donation was infected with a virus, it could contaminate the whole batch.

In England and Wales, the NHS relied on blood products from the US, but as the Aids crisis unfolded, in 1983 newspapers had begun asking questions about the safety of American blood products.

'Russian roulette'

Jason recently discovered that in late 1984 - his father had raised concerns with his doctors about Factor VIII but he says he was told "there was nothing to worry about, this is sensationalism and not to pay attention to it. And he trusted his doctor".

"I think the moment there was a suspicion the Aids virus may be in these products, patients should have been given the choice of whether they wanted to take that gamble and play Russian roulette with their life," Jason says.

Jason is now suing the government for negligence and a breach of statutory duty for "their role in this scandal that ultimately led to infecting my father with HIV for a product they knew to be dangerous".

Des Collins of Collins Solicitors, acting for Jason, says: "This will be the first direct challenge of its type and throughout, our aim will be to support and represent families affected by this scandal."

Two inquiries have been carried out and, in 2015, the then Prime Minster David Cameron apologised to thousands of victims.

The current government has resisted calls for a fresh inquiry but last year it announced more money would be available to those affected by the scandal.

'We became known as the Aids family'

Image caption Janet and Colin Smith say there are still so many unanswered questions about their son's death

It has been 27 years since Janet and Colin Smith's son Colin died aged seven.

Colin was born with haemophilia - but it was the treatment he was given that killed him.

In June 1983, eight weeks before he was first treated, a letter was sent out to haemophilia centres recommending children should be treated with NHS concentrates, not US Factor VIII.

But the guidelines were not followed and Colin was given his first dose of American concentrate shortly before his first birthday. His parents still do not know why.

The couple were eventually told in a hospital corridor their son had tested positive for HIV.

"They said: 'Oh, Colin's tested positive for HIV'. We didn't even know what it was really," Mr Smith says.

The couple say they became known as "the Aids family" and were forced to move. "It was written on the side of the house... just 'AIDS' in big capital letters."

'Stupid or incompetent?'

"Towards the end, we were picking up our son in sheepskin because we'd hurt him - he'd lost so much weight," Mrs Smith says.

They want the government to be held to account.

"Who's to blame? Are they stupid or just incompetent? It's one or the other isn't it? It's somebody's fault," she says.

The couple visit their son's grave twice a week.

"I miss him so much some days... He could have lived a normal life. Such a lovely little boy. Just so unnecessary."

'I'm frightened I'm going to die'

Image caption Michelle says she was made to feel like a "silly child" by her GP after requesting a blood test

In 2015, Michelle Tolley was told she had hepatitis C.

In 1987, she had been given a blood transfusion after haemorrhaging when she gave birth to her first child, and again after giving birth to twins in 1991.

"I was like 'no, no, no... you're telling me I've had hepatitis C for 28 years?' Growing silently - because they call it the silent killer," she told Panorama.

'Made to feel silly'

The NHS had run a campaign to encourage people who might have been given contaminated blood to get tested.

"I went along to my GP at the time to inquire, just to be told 'don't be silly, you won't have that'. It made me feel like a silly little child, that was just wasting somebody's time," she says.

Hepatitis C gave Michelle cirrhosis of the liver - which can cause cancer.

"I get angry days - really, really angry where I feel like I'm being deprived of my life," she says. "And I'm frightened I'm going to die."

Watch Panorama - Contaminated Blood: The Search for Truth on Wednesday 10 May at 21:00 BST on BBC One and afterwards on BBC iPlayer.