Some 1,000 tanks have been built to hold the water. But these are believed to be at around 85% of their capacity and every day an extra 400 tonnes of water are being added.

“The quantities of water they are dealing with are absolutely gigantic,” said Mycle Schneider, who has consulted widely for a variety of organisations and countries on nuclear issues.

“What is the worse is the water leakage everywhere else – not just from the tanks. It is leaking out from the basements, it is leaking out from the cracks all over the place. Nobody can measure that.

“It is much worse than we have been led to believe, much worse,” said Mr Schneider, who is lead author for the World Nuclear Industry status reports.