The Government is being urged to take a hard stance on whaling, after Japanese authorities revealed they'd killed more than 300 whales in their recent mission to the Southern Ocean.
Over half of the whales killed were pregnant females.
The slaughter comes despite a 2014 decision by the International Court of Justice, which ruled that Japan's whaling programme is illegal.
Green Party MP Gareth Hughes says we can't let this fly under the radar.
"We did win the legal case at the International Court of Justice. What you see here is Japan flouting international law. And of course they've been flouting our and Australian waters as they've been passing through it previously," he says.
Mr Hughes says New Zealand needs to patrol the Southern Ocean.
"We think that having an official New Zealand vessel bearing witness to the crime and helping taking the heat out of the campaigners versus the whalers battles down there makes sense, and that's something that we'd urge the Government to be doing the work on now to prepare for next summer."
Foreign Affairs Minister Murray McCully said in a statement today the Government was "totally opposed to Japanese whaling in the Southern Ocean, and participated in the International Court of Justice case against Japan in the hope that this practice would cease".
"The fact that Japan has chosen to resume whaling despite the ICJ judgement against them reflects poorly on Japan's international citizenship. The Government will continue to oppose Japanese whaling in the Southern Ocean in every practical and lawful way."
Japan claims the slaughter was for scientific research.
An adviser to Japan's Institute of Cetacean Research says it is acting according to the ruling of the International Court of Justice.
"The International Court of Justice ruled that Japan's previous research programme, known as JARPA 2, was scientific but was 'not for the purposes of scientific research'," says Glenn Inwood. "The government of Japan immediately ceased that programme in line with the ruling.
"The ICJ did not prohibit research whaling in the Southern Ocean. It clarified the rules around research whaling, which now underpin Japan's latest programme, called NEWREP-A."
He says NEWREP-A is in accordance with the rules of the International Whaling Convention.
"Japan does not need the approval of the IWC nor its members to undertake this programme," says Mr Inwood.