Dumping contaminated wastewater into the sea may be the cheapest way for Japan to deal with its troubles of Fukushima nuclear plant, but the Japanese government's decision completely disregards the human rights and interests of the people in Japan and the wider Asia-Pacific region, said Shaun Burnie, a senior nuclear specialist with Greenpeace East Asia.

Japan's decision will pose a direct threat to the marine environment, and Greenpeace fully supports countries to challenge Japanese government under UN Convention on the Law of Sea, said Burnie.

"Greenpeace is determined to campaign to overturn and to stop this outrageous decision by the Japanese government," said Burnie.