Ministry of Defence scientists face criminal charges over horrifying experiments on service men and women during chemical and biological weapons tests. Detectives investigating the activities at the Porton Down research centre are considering charges which involve assault and administering poison, the Daily Express can reveal.

Police have been investigating the deaths of more than 40 "human guinea pigs" and injuries to more than 400 others at the centre near Salisbury, Wiltshire.

The inquiry team has taken dozens of statements from victims and their families and could arrest and interview former staff in the coming months.

Officers have also seized records said to include film of soldiers unwittingly fed the drug LSD by the scientists.

The investigation, which originally focused on experiments in the Fifties and Sixties, has been widened to include research carried out up to the end of the Eighties.

Yesterday Wiltshire police declined to comment in detail on the progress of the operation, codenamed Antler and led by Detective Superintendent Gerry Luckett.

But a Daily Express investigation has revealed the gravity of the actions investigated by the Antler squad.

Survivors of the scandal claim they were tricked into taking part by being told the tests were to find a cure for the common cold.

They claim they were impregnated with deadly chemical agents such as sarin and mustard gas and mind-bending drugs such as LSD.

One volunteer, airman Ronald Maddison, died after having sarin dropped on to cloth wrapped round his arm in May 1953.

Police originally focused their inquiry on his death but later began examining the cases of other subjects who had died from mystery illnesses after leaving the centre.

Many of those who lived through the ordeal suffered a lifetime of complicated medical problems which are almost certainly related to their treatment. One witness said Royal Marines were given LSD then ordered to simulate an attack on an enemy position. The resulting chaos was filmed.

A survivor said he had sarin - the agent developed by the Nazis and used to kill 12 commuters in an attack on the Tokyo subway five years ago - squirted into his eyes.

Another alleged victim, now 55, said he was ordered to take part in the experiments under threat of court martial. During three nightmare weeks at the centre, he said he was stripped to his underpants and marched repeatedly into gas chambers where he was impregnated with sarin, tabin and mustard gas.

He also claims he was given hallucinogenic drugs and, after leaving the service to resume civilian life, suffered a catalogue of health problems, including flashbacks and renal failure.

Many of the Porton Down subjects said they were forced to sit in gas chambers with white rabbits on their laps, in a bid to test how long after the animals' deaths humans could tolerate the poison. One of the few recorded women to be used as a guinea pig claims she suffered complications with the birth of her two children after helping to test a valium-based drug.

Another survivor, Ken Earl, is planning to set up a support group for victims who want to know more about what happened and how to seek compensation.

Mr Earl, 67, was at the centre at exactly the same time as Mr Maddison and endured the same procedure of having 200 milligrammes of sarin dropped on to his arm.

He said: "My long-term health has been ruined by what happened to me at Porton. None of us knew what we were in for when we got there and we just went along with it because we obeyed orders.

"I don't think the British public realise what has been done in their name. They imagine that it's Nazi or Soviet scientists who did this sort of thing. Well, sadly, they're wrong.

"Many of us have been trying to bring this out into the open for years but it's only since the Wiltshire investigation that things seem to have moved at all.

"It's time the Ministry of Defence put their hands up and at least admitted that things were done very wrongly.

"They should compensate a group of loyal people who were treated most inhumanely.

"We also hope that individual scientists are going to be brought to account for their actions. Many of them must still be involved in scientific work.

"What happened to us displayed the callous indifference of the Porton Down scientists. You wouldn't treat a dog the way they treated people."

Solicitor Alan Care, who represents 77 ex-forces personnel seeking compensation, said: "It's horrifying stuff. A whole variety of very nasty things were administered to service people, the vast majority of them men, over a long period of time right up until the end of the Eighties.

"They were duped and subjected to a whole range of chemical and biological warfare agents without their consent and without any knowledge of what they were given.

"Almost without exception they all subsequently suffered from a whole range of chronic illnesses.

"Proving the link between what happened to someone and the illnesses they then suffered from is notoriously difficult, but proving they were treated in a way that amounts to assault is less difficult."

A police spokesman said yesterday: "The Operation Antler investigation is still under way and we will not comment as that might prejudice any future proceedings."

A spokeswoman for the MoD said: "We will not comment on anything related to the criminal investigation into Porton Down except to say we are co-operating fully with Wiltshire police."

I'm in constant pain

RAY Hutchins, 66, claims he suffered the horror of having sarin directed into his eyes.

Mr Hutchins was an 18-year-old gunner with the Royal Artillery when he volunteered for what he thought was work on the common cold. The reward of 15 days' leave and extra pocket money was too good to refuse. "We were put into gas-proof clothing and a mask, and everything was covered apart from our eyes," he said. "We went into gas chamber with a sort of glass honeycomb wall and there was mist in there. They kept us in for three minutes and the pain on my eyes was immediate and incredible. Now I know it was sarin."

Mr Hutchins, of Stoke-on-Trent, said: "When I left Porton I went blind as I waited at the bus stop. This turned out to be temporary, but I have lived with constant pain behind my eyes ever since."

THEY JUST DIDN'T CARE

CHRIS Mablon, 42, thought he too was helping with cold research. But he said he was among volunteers put into a chamber several times and given sarin and mustard gas.

"We were lied to, it's as simple as that," he said. "One of the RAF lads reacted particularly badly. You could see he was seriously damaged. It was pitiful but the scientists just didn't care. The mustard was put on strips of cloth designed for protective clothing that had been taped on to you and they were testing for reactions."

Mr Mablon, of Sutton Coldfield, West Midlands, added: "My grandad was gassed with mustard in the First World War and his lungs shot to pieces. So I wondered why the hell they needed to do that research with humans. The mark the mustard left on me was awful, a huge abscess eating into me. I've had terrible skin and chest problems since."

WE WERE VERY NAIVE

KEN Earl, 67, endured the same experiments as Ronald Maddison, the airman who died in 1953. Mr Earl had 200 milligrammes of sarin dropped on to strips of uniform material wrapped round his arm. He has suffered a catalogue of medical problems, including liver and skin complaints.

"They told us to bare our arms then then taped two lots of material on," he said. "They then dropped from a pipette 10 drops of each of this colourless liquid which turned out to be sarin. My total dosage was 200 milligrammes. When they did it to Ronald Maddison two days later, it killed him."

Mr Earl, an actor who has appeared in TV series including Minder and Z Cars, added: "I had never heard of Porton Down and didn't know what it was. We were very naive and didn't think our superiors would send us on something so dangerous."