New Zealand's led an international protest in Tokyo against Japan's plans to resume killing whales in the Southern Ocean.

Backing New Zealand up the US, Australia, Mexico, South Africa and other EU member countries joined in the formal action.

Ambassador to Tokyo Mark Sinclair led the delegation in delivering a strong formal message from 33 nations.

It was that there's no scientific basis for the slaughter of whales, and Japan's being strongly urged not to allow it to go ahead.

Australia also said it's considering further legal action.

A Japanese whaling fleet set sail for the Antarctic last week, despite environmentalists slamming the move as a "crime against nature".

Tokyo plans to kill 333 minke whales for scientific research this season, despite a worldwide moratorium and opposition led by Australia and New Zealand.