In its report "Secure energy, civil nuclear power, security and global warming", the Oxford Research Group said there was not enough uranium available and nuclear nations would therefore tend to opt for reprocessing spent fuel to obtain plutonium.
"A multiplication of reprocessing and the resulting international trade in weapons-useable materials would create more opportunities for states, criminal organisations or terrorists to acquire weapons-useable materials," it said.
Juergen Trittin, former German environment and nuclear safety minister, writing a foreword to the report, said the spread of nuclear power technology would automatically lead to weapons proliferation, threatening global security.
"One of the worst ideas, circulating in many corners of the global discussion, is the call for an expansion of nuclear power as a means of climate protection," he wrote.
"The recommendation is a clear-cut case of fighting one risk with an even bigger one. The risks of proliferation and nuclear terrorism by both state and non-state actors are simply uncontrollable," he added.
Not only that but extraction and purification of uranium was carbon-intensive even if nuclear power plants themselves emit little, and thousands would need to be built to make a serious impact on the battle against climate change, the report said.
With scientists predicting that average temperatures will rise by up to 4.0 degrees Celsius this century because of carbon gases from burning fossil fuels for power and transport, nations are anxiously casting around for quickly available alternatives.
Nuclear provides 80 percent of electricity in France and 20 percent in Britain, and the governments in both have said the plants should be replaced with new ones when they are retired. Other nations are also looking favourably at nuclear power.
Environmentalists say renewables like wind, waves, solar and hydro can do the job better and more cleanly, pointing to security and saying nuclear waste remains deadly for generations.
The nuclear lobby has repeatedly rejected the arguments on the grounds that none of the renewable technologies offer guaranteed power supply.
Nuclear proponents also say nuclear plants are secure from attacks -- even like those on Sept. 11, 2001 in New York and Washington.
At present only a handful of countries carry out reprocessing, including Britain, France and Japan. But the boom in demand if nuclear power does take off could mean a rapid spread and therefore reduced control, the report said.
At the same time, the warming of the climate bringing increased floods, famines and violent storms risked also raising political instability and insecurity in the worst hit regions just when they might be acquiring nuclear technology.
"Nuclear power cannot make a major contribution to global reductions in carbon dioxide emissions, whereas its effect on global insecurity and the risks of catastrophic conflict or terrorism are there for all to see," the report concluded.