The Greens want a marine protected area being set up in the Ross Sea area of Antarctica to be properly policed and to last for longer than planned.

A joint bid by New Zealand and the United States to create the world's largest marine protected area in the Antarctic succeeded after four years of negotiation.

Foreign Minister Murray McCully on Friday hailed the breakthrough, saying the 25-nation Commission for the Conservation of Antarctic Marine Living Resources reached unanimous agreement at a meeting in Hobart.

The protected area is in the Ross Sea region of the Antarctic.

"It will cover roughly 1.55 million square kilometres, of which 1.12 million square kilometres will be a no fishing zone," Mr McCully said.

The Greens say New Zealand should push for a longer period than the 35 years in the agreement.

Greens Co-leader James Shaw also wants the National government to make sure there is proper monitoring.

Fishers have flouted the law and been let off the hook by Ministry of Primary Industries officials in recent times.

"Let's make sure that the sanctuary is policed properly from the get-go," said Mr Shaw.

He says the government should made the same kind of commitment to New Zealand's Exclusive Economic Zone, which is one of the largest in the world, and "which the proposed Marine Protected Areas Act won't preserve".

The Antarctic protected area comes into force on December 1 next year.

The Antarctic Ocean Alliance applauded the "momentous agreement".

Greenpeace said it was a victory for the millions of people who had supported the campaign.