Environmentalists say the possibly catastrophic failure of a Japanese nuclear reactor shows that nuclear power can never be safe.
Two reactors at the Fukushima plant in north-eastern Japan have been damaged by the devastating earthquake which struck nearby on Friday, and at least one is in danger of meltdown.
Radiation has been released into the air after an explosion at one reactor, and although authorities have said it is not intense enough to affect human health, they have ordered evacuations of people living within 20km.
"This proves once and for all that nuclear power cannot ever be safe," Greenpeace campaigns head Steve Campbell said on Monday.
"Japan's nuclear plants were built with the latest technology, specifically to withstand natural disasters, yet we still face potential meltdown," he said in a statement.
Greenpeace was also concerned about the lack of information about the total amount of radiation already released, and whether the ponds for spent radioactive fuel - outside the containment area of the reactor - were secure.
"We request that Japan's government share this information with the public immediately," he said.
Anti-nuclear campaigner Helen Caldicott said the release of radioactive caesium 137 and iodine 131 into the atmosphere from the Fukushima plant posed grave health risks.
If a meltdown occurred, 200 other isotopes would be released, she said in a statement.
"All of these substances can cause cancer and genetic diseases either in the near or long term," said Ms Caldicott, who is president of the Foundation for a Nuclear Free Planet.
Earthquakes were not unknown in Australia, she said.
"Are we mad enough to introduce this disastrous form of energy into our lives?"
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