Nuclear reactors of the kind France wants to sell to Britain suffer from "potentially catastrophic" problems, it was claimed yesterday.
News of the structural flaws came days after President Nicolas Sarkozy used a state visit to Britain to boast about his nation's nuclear expertise.
He made it clear that devices such as the European Pressurised Reactor (EPR) being built at Flamanville, in Normandy, should be on Gordon Brown's shopping list as part of the "entente formidable" between the two countries.
But a letter from France's nuclear safety watchdog, ASN, leaked on a website yesterday, highlighted weaknesses that could undermine the £2.8 billion project.
Pointing out "numerous malfunctions" in the building of the reactor at Flamanville, it calls for them to be corrected in a month. These include weaknesses in steel grids reinforcing the concrete base supporting the reactor.
Such damage could lead to nuclear accidents, threatening the population of northern France, the Isle of Wight and possibly the coast of England.
The Prime Minister and Mr Sarkozy pledged last week to co-operate "on a new generation of nuclear power plants by sharing information on safety, security and waste disposal."