Environment minister Tse Chin-wan on Thursday said Hong Kong will immediately ban imports of aquatic products from parts of Japan if authorities there go ahead with a plan to discharge wastewater from the stricken Fukushima nuclear plant into the ocean.

Writing in the Ta Kung Pao newspaper, Tse said the recent discovery of a fish from the Fukushima area containing an excessive amount of the radioactive element caesium shows the discharge would pose a serious risk to food safety.

He said Hong Kong officials would take strict measures to protect public health, including a ban that would apply to aquatic imports from Fukushima and the nearby coastal provinces. He added that imports from other parts of Japan that are at risk of contamination would be subject to strict control.

Testing of Japanese food is also being stepped up, he said.

Tse called Tokyo irresponsible, saying it has been pushing ahead with the discharge plan despite grave concerns among the international community.

"If the Japanese government is confident about the safety of the processed nuclear wastewater, it should find uses for it locally like irrigation, instead of discharging it into international waters and causing an extensive food safety risk," he wrote.

The minister said officials have asked the Japanese authorities not to release the wastewater before there is an international consensus on the matter.