An inquiry into the cases of servicemen used as "guinea pigs" in chemical weapons tests has decided there is insufficient evidence to warrant a criminal prosecution.
The inquiry has lasted four years and cost millions of pounds
The men took part in tests at the Porton Down research centre in Wiltshire over a 30-year period from the 1950s to the 1980s.
A Wiltshire Police investigation into the cases has revealed there was criminal liability arising out of the conduct of some former scientists.
But lawyers have decided there is not enough evidence to charge anyone.
Lawyers acting for some of the ex-servicemen involved say they may take the case to the civil courts as evidence from the recent investigations can be used in a civil action, it is believed.
The decision not to prosecute has angered veterans who claim they were duped into volunteering for the tests.
Former serviceman and test survivor Gordon Bell, from Sunderland, said: "I am absolutely outraged - we have the evidence, we have lots of witnesses.
"There is no reason why they should not prosecute.
"What they did to people was a disgrace to this country - it was parallel to the Nazi experiments carried out in concentration camps."
He claims that substances being tested for chemical weapons were dripped on to his skin.
Mr Bell has also claimed that Aircraftsman Ronald Maddison, from Consett, Co Durham, died in May 1953 when a nerve agent was dripped onto his arm.
The inquest into his death is due to start on 30 September 2003.
Ella Foster, 83, whose father was Mr Maddison's cousin, told BBC News Online: "It is a bit disappointing but the families have done all they can. I did think they might have tried to bring a prosecution.
"But it may well be that they think too long has elapsed, or that those responsible are no longer alive."
Campaign groups representing veterans interests argue that servicemen were told they were helping with research into the common cold.
But many of them died after being exposed to deadly nerve agents and other toxic chemicals.
Porton Down veteran Ken Earl said: "I am very disappointed, but not entirely surprised.
"I am particularly disappointed for the veterans who have been treated so shabbily by a government which they served without question.
"Who was it at the MoD who authorised these chemical and biological tests to be carried out on naive and unsuspecting servicemen and women?"
A statement from Wiltshire Police read: "Chief Constable Dame Elizabeth Neville has written to over 700 former service personnel, or their next of kin, who have had contact with the Police investigation, concerning their participation in the human experimentation programme at Porton Down.
"The Chief Constable outlines the investigation conducted by Wiltshire Police and the result of the Crown Prosecution Service (CPS) decision.
"The decision of the CPS, based upon the evidential files they have reviewed to date, is that no individual will be prosecuted for any criminal offence," it concluded.
The Wiltshire Police investigation - codenamed Operation Antler - was launched in 1999 and is believed to have cost £2m.