The Ministry of Defence admitted claims by the Campaign for Nuclear Disarmament that the radiation experiments had been conducted, but insisted they were "ethical".
Janet Bloomfield, the outgoing CND chair, claimed the tests involved volunteers inhaling, eating or being injected with a number of radioactive substances.
She added that some of the tests, at the Atomic Energy Research Establishment at Harwell and the Atomic Weapons Establishment at Aldermaston, were still going on.
The tests began in 1957, she said. "The Government has consistently misled Parliament, the public and those involved about what has been done."
Full details of CND's allegations are published today a report entitled Nuclear Guinea Pigs, which draws on more than 50 documents from the Ministry of Defence and other government departments as evidence that the tests, involving about 10 radioactive substances, have been going on since 1957.
It was written by CND researcher Eddie Goncalves, who earlier this year helped expose secret official documents about radioactive contamination at Greenham Common.
"Experiments are supposed to have been carried out on volunteers," Mr Goncalves said. "But one of the issues here is to what extent these guinea pigs really were volunteers and to what extent they had the risks properly explained to them."
The Ministry of Defence confirmed the radiation experiments had taken place but insisted they were "ethical". A spokeswoman said: "There is no evidence of any MoD involvement in unethical radiation experiments on humans.
"Studies involving the use of radioactive material have been carried out at Harwell, Aldermaston and Porton Down, some of which go back to the Fifties and Sixties. Some recent studies were conducted in the Eighties."
She said that a total of 200 volunteers, including MoD civilians and military personnel, had been involved in the tests, and denied CND's claims that the tests had involved eating radioactive substances.
"None involved the inhalation of plutonium. Other substances administered were negligible," she said.
"All studies involved volunteers who had the opportunity to pull out at any time. They have been subject to proper medical safeguards and with the full knowledge of the persons concerned.
"They were talked right through what the tests involved. They were told the tests were absolutely safe."
"The studies have been conducted with the aim of either furthering medical science or testing operational equipment."
She also denied people were pressurised into taking part.
The spokeswoman said: "There were no fatalities or illnesses. The tests were done in the interests of protecting the future safety of people."
Last night, a spokesman for CND said that the anti-nuclear group's claims were backed up by documents released by the American government detailing human radiation experiments.
CND said these documents showed that British volunteers were not given consent forms and included a man of 82. This compares with the treatment of American volunteers, who had to sign consent forms and a bill of rights, said the spokesman.
The spokesman said: "Aldermaston denied in 1994 that it had been involved in human radiation experiments. These documents prove that's not true.
"The British Government put tremendous pressure on people to agree to take part in these tests. Many were civil servants who were recruited from various departments."
He added that CND is now calling for a royal commission to investigate these experiments, which the organisation claims are still being carried out by the Ministry of Defence.