By Severin Carrell

 Scientists who conducted nerve gas tests on thousands of soldiers at the Porton Down chemical warfare laboratory are to face prosecution for allegedly poisoning volunteers with deadly weapons such as mustard gas and sarin.

Wiltshire police believe there is enough evidence to charge up to five retired scientists with criminal offences linked to secret nerve gas and chemical warfare trials carried out during the 1950s and 1960s at the plant on Salisbury Plain.

In an unprecedented move the force is to ask the Director of Public Prosecutions, David Calvert-Smith QC, to take the scientists to court for allegedly duping volunteers into taking part in the tests.

The historic case, which follows a two-year inquiry by a team of 30 Wiltshire and Ministry of Defence detectives, is the first time any government scientist has faced prosecution for carrying out officially sanctioned research.

Alan Care of the law firm Russell, Jones and Walker, who represents 400 former Porton Down veterans, predicted the scientists would be charged with administering poisons without consent under the 1861 Offences Against the Persons Act. "This vindicates everything we have been saying for the last seven years," he said.

The decision to prosecute follows allegations that at least one volunteer, Ronald Maddison, 20, was killed and scores of others suffered serious illnesses, including respiratory illnesses, serious skin complaints, poor eyesight and heart and lung problems, as a direct result of the tests. Many veterans, most of whom were National Servicemen, said they volunteered after being told the tests were to find a cure for the common cold. In fact, they were dosed with nerve agents and chemicals such as sarin, VX gas, LSD, mustard gas, CS gas and artificial smog.

The police interviewed about 650 servicemen and next of kin who allege the volunteers suffered ill health due to the trials. After investigating the deaths of 40 volunteers, the police also believe they found evidence they suffered unusual levels of ill health and premature death.

Police also formally interviewed five scientists under caution in April. As a result of their investigations, a fresh inquest into the death of Maddison, who was killed in 1953 after 20 drops of sarin were dropped on a patch on his arm, is expected to be held by the Wiltshire coroner, David Masters. The original inquest was held under strict secrecy and found Maddison died of asphyxia. The coroner has asked the Attorney-General, Lord Goldsmith, to quash the findings before he can hold the new inquiry.

The decision to seek prosecutions was inadvertently revealed by the Ministry of Defence in a briefing document for medical researchers who are bidding to carry out a major study into the rate of illness and death amongst Porton Down volunteers.

The document says: "Recently the police have begun to interview under caution former Porton Down employees about their involvement in the trials. They have informed us that some cases will be referred to the Crown Prosecution Service later this year."

The MoD refused to comment on the police inquiry, but a spokeswoman said: "We have no scientific or medical evidence that participating in these tests led to long-term medical or health problems for those volunteers."