"In each of the four attack scenarios that I examined, the plant fared very badly indeed - if these scenarios had been for real, then there would have been the potential for a major radioactive release," said British atomic expert John Large in his report.
The report followed a number of unexplained, but apparently co-ordinated, flights of tiny, unmanned vehicles over French nuclear installations, the Independent reported.
"The grave issues uncovered there, said Large, were equally relevant to the UK's 16 operational reactors, which generate about 18 per cent of the country's electricity," the paper said.
Large's modelling showed that the "flexible access and manoeuvrability of the drones" means that they were able to fly over and twist around physical barriers that "belonged to a different age".
Even small, battery-powered drones can lift 10 or more kilograms of cargo, while vehicles available in high street hobbyist shops are "certainly not toys but machines capable of following and discharging intelligent commands".
British officials have looked at Large's evidence and forwarded it to the Office for Nuclear Regulation, but have not requested a copy of the report itself, the paper said.
Such incidents have occurred in restricted airspace over 13 French nuclear plants since October. On one evening, there were five co-ordinated flyovers at stations located hundreds of miles apart.
Although the vehicles are believed to be commercial and civilian in nature, there are fears that a terrorist group might be using them for surveillance to evaluate the security of France's 19 nuclear sites, the paper said.
David Lowry, a consultant researcher for the World Institute for Nuclear Security in Vienna, said: "My general view is that all nuclear facilities are at risk of malevolent terrorist attack."
Citing a senior Whitehall source, the paper said that the government has increased its focus on nuclear security against "all threats".
