A wildlife advocacy group says koalas should be relocated to New Zealand eucalyptus plantations to prevent them from becoming "functionally extinct".

The ongoing bushfire crisis has killed as many as one billion animals, including koalas, according to the most recent estimate by University of Sydney expert Professor Christopher Dickman.

Now, a group called the Koala Relocation Society is saying the native Australian animals could "thrive" in New Zealand.

"Koalas are functionally extinct in Australia, and could thrive in New Zealand, as many other Australasian species do," it said in a statement.

In the video below: Carload of koalas rescued on Kangaroo Island

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"They would not compromise our local eco-system, as koalas typically inhabit open eucalypt woodlands, and the leaves of these trees make up most of their diet.

"New Zealand has 28,575 hectares planted in eucalypts, most are located in the Central North Island, and are similar to much older forests from Australia, as they grow fast here."

Vets and volunteers treat Koalas at Kangaroo Island Wildlife Park. Credit: DAVID MARIUZ / AAPIMAGE

However, a spokesperson for Prime Minister Jacinda Ardern said their priorities are elsewhere.

"Our focus is getting the fires under control so they [the koalas] can stay in their natural habitat," the spokesperson told local outlet 1 NEWS.

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"Ms Ardern is currently on leave while Parliament is shut for the holidays but has been maintaining an active watch on the situation with the fires, including keeping in contact with the Australian Prime Minister, Scott Morrison."

Nonetheless, the petition to bring koalas to New Zealand has surpassed 6,000 signatures as of Monday morning.

Hundreds of koalas were taken to Kangaroo Island Wildlife Park for treatment. Credit: DAVID MARIUZ / AAPIMAGE

It comes as parts of Australia experience a brief, albeit welcome, reprieve from the fires.

Firefighters in both New South Wales and Victoria are using cooler conditions to strengthen containment lines.

They've been joined in recent weeks by firefighters from New Zealand and the US as hundreds of thousands of hectares of land burned.