A remote island home to some of New Zealand's most threatened species has been officially declared predator free.

Antipodes Island, in the Subantarctic, was the target of a years-long effort called Million Dollar Mouse, aimed at protecting the many bird and insect species living there from mice.

Around 200,000 mice were believed to be on the island, after the species first arrived more than a century ago.

CHARLIE MITCHELL/STUFF A pair of Antipodean wandering albatrosses, a critically endangered species.

The project was described as one of the most complex island eradications ever undertaken, and involved shipping helicopters and diggers to Antipodes, which is 760km from Dunedin, building a temporary hangar, and covering the 2000ha island with bait.

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Some of the island's species include the critically endangered Antipodean wandering albatross, the erect-crested penguin, and two species of parakeet, all of which are found nowhere else.

CHARLIE MITCHELL/STUFF A parakeet on Antipodes. The island has no trees, so they forage on the ground.

Some of the bird species were competing with mice for food, which posed a long-term threat to their survival. There is also evidence from other islands that mice can prey directly on seabirds.

The Subantarctic islands as a whole are a World Heritage Area, which obliges New Zealand to protect their internationally significant values.

A monitoring team on Tuesday returned from a three-week stay on Antipodes, joined by two conservation dogs, and said their work showed no mice remained.

CHARLIE MITCHELL/STUFF A large penguin colony on Antipodes. The little-studied erect-crested penguin is only found here and on Bounty Island.

"This is huge news for conservation both in New Zealand and internationally," Conservation Minister Eugenie Sage said in a statement.

"The successful Antipodes Island mouse eradication is another landmark conservation achievement which underlines DOC's technical expertise in pest control and threatened species protection."

The project was led by the Department of Conservation (DOC), with funding support from the Morgan Foundation, Island Conservation, the World Wildlife Fund, and public donations.

Million Dollar Mouse's project manager, Stephen Horn, said the successful operation had built upon other eradications in the past.

"The success of this project was built on the lessons and experience from many other island eradications in New Zealand and abroad," he said.

"The Subantarctic islands are remote, but the role they play in global conservation as the home for so many unique species can't be overstated."

A feasibility study is underway for clearing the Auckland Islands of predators, which include pigs, cats and mice. Campbell and Enderby islands, both in the Subantarctic, have already been cleared of predators.

- Read more about Antipodes Island in 'The Island', a Stuff special feature