British authorities gave interim approval on Wednesday for designs for two nuclear reactors proposed for construction by French firms EDF and Areva, and by US firm Westinghouse.

The Office for Nuclear Regulation and the Environment Agency said they were were "satisfied with how the designers of both EDF and Arevas UK EPR and Westinghouses AP1000 reactors plan to resolve a number of remaining issues.

"Neither reactor can be built in the UK until these issues are resolved."

The firms had to detail their plans for conforming with strengthened security measures adopted by Britain in October after the Fukushima disaster in Japan but a statement did not specify the measures to be taken.

Kevin Allars of the Office for Nuclear Regulation said: "We have reached an important milestone."

"This interim acceptance confirms that all the plans on how the industry will resolve the outstanding issues are in place. This includes how they will address matters raised in the chief nuclear inspectors report, published in October, on lessons learnt for the UK from Fukushima."

He added: "It is for the designers now to satisfy us that they have resolved these issues. We will not allow industry to build the reactors until they have done so."

EDF wants to build two reactors at Hinkley Point in Somerst, southwest England. The first reactor would enter service in late 2018 or early 2019 and the second in 2020 according to the firm's plan.

Britain has 10 nuclear power stations with 19 reactors, producing nearly a fifth of the country's electricity.

Unlike Germany and Italy which decided to abandon nuclear power after Fukushima, the government of Prime Minister David Cameron is pushing ahead with it while adopting tighter safeguards in light of the Japanese nuclear crisis.