Some trials of chemical agents on human volunteers at Porton Down laboratories were "unethical", according to a report published by the Ministry of Defence.
Tests on human volunteers were carried out until 1989
The report says a number of tests in the 1940s and 1950s involved "serious departures" from the ethical standards that should have been observed.
But the report's independent ethical assessor said concerns related to only a few of the hundreds of tests done.
Sir Ian Kennedy said they had never gone beyond what should be tolerated.
Professor Kennedy oversaw the work of MoD officials conducting a historical survey of tests at Porton Down, launched in 2000 in response to the concerns of veterans that they may have suffered lasting damage to their health.
He said there was "no evidence to justify a conclusion that the conduct of the trials at any point went beyond the limits of what should ever be contemplated, far less tolerated, in a civilised society".
Among the tests Professor Kennedy highlighted which he felt may not have met ethical standards were:
Trials of liquid nerve agents on bare skin, carried out between 1951 and 1953, including one test which led to the death of 20-year-old Leading Aircraftman Ronald Maddison in 1953
The trials in 1951 of the nerve agent GD, in which the lethal dose was not known with sufficient certainty
The trial in 1958 of the nerve agent VX, which involved the use of what, at the time, was regarded as the lethal dose
The trials in 1942 involving the exposure of volunteers to H vapour in the scrotal region, in which he said it appeared likely volunteers gave no real consent
The trial in 1945 of a substance from captured German shells, which exposed volunteers to danger without first seeking to determine the nature of the substance
He also said there were "question marks" over experiments carried out from the 1950s to the 1970s in which the eye condition miosis was artificially induced, which he said "might be said by some to have constituted too great a step into the unknown".
But Professor Kennedy said the tests were carried out in "a thorough, painstaking, careful and often ingenious manner" and were "obviously of great importance in assessing military effectiveness".
And he cautioned against judging the researchers involved against the moral standards of today's comparatively peaceful world.
"The work was conducted at Porton in difficult times," he said.
In response to the report, the MoD said in a statement: "These trials must be viewed in the context of the Second World War and the Cold War and their associated pressures.
"The nation was facing a real threat and these trials were essential for national security in that context.
"Much has changed in law and ethics in the half century since many of these experiments and there is a danger in seeking to apply today's standards when those reflect evolution over that period and did not represent the prevailing standards at the relevant time."
It added: "The Ministry of Defence is very grateful to all those whose participation in studies at Porton Down made possible the research to provide safe and effective protection for UK Armed Forces."