The leak at the Fukushima nuclear plant has now been classified at the same level of severity as the Chernobyl disaster of 1986, an official acknowledgement that there has been a major release of radiation.

The move reflected the fact that there was a "significant" risk of radioactivity getting into the environment, David Weaver, professor of nuclear physics at Birmingham University, told the programme.

Environment analyst Roger Harrabin said that international "dissatisfaction" with the information getting out of Japan was adding to the problem.

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