Earthquake warnings in place since 2008

London: Japan was warned more than two years ago that its nuclear power plants could not withstand powerful earthquake, leaked diplomatic cables have disclosed.

Safety rules were out of date and strong tremors could pose a "serious problem", an official from the International Atomic Energy Agency (IAEA) said in December 2008.

The Japanese government promised to upgrade safety at all of its nuclear plants, but will now face questions over whether it did enough.

It responded by building an emergency response centre at the now-stricken Fukushima plant, but that was only designed to withstand magnitude 7.0 tremors.

Friday's earthquake, 81 miles off the coast, was of magnitude 9.0.

The news is likely to put further pressure on Naoto Kan, Japan's prime minister, who has been criticised for "dithering" over the crisis at Fukushima.

Panic spread throughout Japan yesterday following news that a third explosion might have damaged the protective casing around a reactor core, increasing the threat of radioactive leaks.

Concerns about safety at nuclear power plants in Japan, one of the most seismologically active countries in the world, were raised during a meeting of the G8's nuclear safety and security group in Tokyo in 2008.

A US embassy cable obtained by the WikiLeaks website disclosed how the Japanese government opposed a court order to shut down another nuclear power plant in western Japan because of concerns it could not withstand earthquakes above magnitude 6.5. However, a cable from March 2006 reported that the court's concerns were not shared by the country's nuclear safety agency.

The government successfully overturned the ruling in 2009.