French authorities deliberately exposed soldiers to nuclear testing in the Sahara, according to researchers citing a confidential French military report.
At least one test aimed to "study the physiological and psychological effects of nuclear arms on man", they say.
Le Parisien newspaper, which carried excerpts from the document on Tuesday, quoted the defence minister as saying he had no knowledge of the report.
Some soldiers say they were made ill by French tests dating back to the 1960s.
They have complained for decades that they were given insufficient protection from radioactive fallout during testing, with some claiming they were used as "guinea pigs".
After long denying any responsibility, the French government drew up a bill last year to compensate veterans for health problems that could be linked to the tests.
Researchers at the Armaments Observatory in Lyon, a non-governmental research group that has worked closely with French veterans of the nuclear tests, said the report they cited was written in the late 1990s as an overview of French testing, and drew on secret military documents.
It describes official interest in studying "the physiological and psychological effects of nuclear arms on man" in connection with France's fourth atmospheric test, Gerboise Verte, on 25 April 1961.
It says "foot soldiers" were deployed in "tactical exercises" during the test, in an attempt to measure the possibility of mounting a military operation in the aftermath of a nuclear attack.
The men were made to approach to within a few hundred metres of the blast site shortly after the explosion.
Patrice Bouveret, a researcher at the Armaments Observatory, said the report was the most explicit indication so far that French authorities had knowingly exposed test participants to dangerous side effects.
"Up till now we had never had direct account of 'foot soldiers' being used in these manoeuvres," he told the BBC.
"[The French authorities] knew that they were putting them in danger when they sent them on these manoeuvres and at the very least they should have taken measures to protect their health."
Defence Minister Herve Morin was quoted by Le Parisien as saying he had no knowledge of the report, while stressing that the level of radiation to which participants were exposed was "very weak".
The French parliament approved the government's bill to compensate veterans last month.
But veterans have complained that its provisions are too restrictive and that only a fraction of those affected will be eligible for compensation.
They are lobbying for the law to include more tests, a broader geographic area, and a greater number of illnesses, when it comes into force later this year.
They also want provisions for environmental clean-ups.
The French carried out 17 nuclear tests in the Algerian Sahara in the 1960s.
France later switched testing to French Polynesia, where a further 193 tests were completed before it ended the practice in 1996.