Parliament will be presented with proposed legislation which would see the New Zealand Defence Force monitor Japan's annual whale slaughter on the southern seas.

Green Party MP Gareth Hughes is penning a private members' bill which would seek to amend the Defence Act 1990.

The modification would see a Naval vessel accompany the Japanese hunting fleet, a move Hughes said would ensure the safety of protest vessels trying to disrupt the whaling.

The mooted law change will be placed into the private members' bill ballot when Parliament resumes next month.

''Arguably it is one of the functions under the Defence Act anyway. But this would just make it explicit,'' Hughes told Fairfax Media.

''It shows New Zealanders care and we are sending a strong message to Japan. It is like when [Norman] Kirk first sent a frigate to Mururoa Atoll .th.th. it is about bearing witness to an environmental crime.''

The NZDF occasionally conducts surveillance patrols of New Zealand's economic exclusion zone and the Southern Ocean.

In its 2011 annual report it refers to ''whale fleet surveillance'' by an Air Force Orion during 2010-11.

The Green Party has repeatedly called for the Government to send a Navy vessel to follow the Japanese whalers and accompanying protest vessels in the Southern Ocean.

Hughes said such a move would send Japan a ''strong message''.

But those approaches had been consistently knocked back.

''We need more than just words to save the whales,'' he said. ''Diplomatic pressure has failed. At this point in time, the best thing the Government can do to save the whales is to ensure the safety of protest vessels trying to stop the hunt.''

Hughes' proposed legislation comes a week after three Australian activists were detained by the crew of a Japanese whaling ship after clambering onboard the Shonan Maru II.

After the trio threatened to go on a hunger strike, Japanese officials agreed to hand the protesters to an Australian coastguard vessel.

Last year, the Japanese government cited the tactics of anti-whaling protesters, mainly Sea Shepherd, for cutting short its annual whale hunt.

Japan's whale fleet had hoped to harpoon 850 whales between December 2, 2010, and early March, 2011. But the boats were recalled about a month early, with whalers reportedly only catching about 170 mammals.

Hughes said he had hoped the increased protest actions, coupled with financial issues at the Institute of Cetacean Research Japan's whaling body would lead the Japanese government to suspend its 2011-12 hunting season.

''Unfortunately their government has bailed them out with a $28 million injection,'' he said. ''They are also putting Japanese security forces on the ships. If anything, they have gone down there escalating tensions.''