The issue of safety rules has also cropped up as the EU is set to expand to take in former communist countries which still run nuclear plants designed and built in Soviet days and which are considered below Western standards.

The European Commissioner in charge of energy policy, Loyola de Palacio, said she aimed to propose "as soon as possible" mandatory standards for nuclear plants throughout the EU.

"It is now high time to go further and propose a community dimension for nuclear safety in Europe which will contain common standards and control mechanisms which will guarantee throughout Europe the application of the same standards," she told a European Parliament committee.

The issue of nuclear power is divisive, with environmentalists strongly against it, and many EU states aiming to phase it out.

De Palacio has said she favours nuclear power as an important source of greenhouse gas-free energy, but the choice of energy source has always been left up to member states.

De Palacio said she wanted a safety standard for the whole EU to be applied just as strictly to the countries, mainly from eastern Europe, which want to join the EU.

She also indicated that the issue of nuclear safety was not being taken seriously enough by those officials who are negotiating with the candidate states, busy concluding talks in various policy areas known as chapters.

"It is possible that technically we give the impression that we are advancing things by closing chapters but in fact we are opening wide a door of concerns and uncertainties," she said.

She noted that Bulgaria, Slovakia and Lithuania had been asked by the European Union in 1999 to shut down their nuclear plants.