Protected oceans around Australia's subantarctic Heard and McDonald Islands would expand by 300,000 square kilometres under a federal government proposal.
The World Heritage-listed islands, 4000km southwest of Western Australia and 1700km north of Antarctica, are home to penguins, seals, whales and albatross.
The expansion would extend protection over important marine environments and help protect globally significant habitat for endangered seabirds and seals, while allowing commercial fishing to continue.
But WWF-Australia says strong protection is still missing for many key conservation areas and risks from fishing would remain.
Few places on earth could be described as pure and pristine wilderness, Environment Minister Tanya Plibersek said.
"Heard and McDonalds Islands is such a place," she said.
"Quadrupling the size of the Heard and McDonald Islands marine park would protect more of our oceans around the island and seals, albatross and whales, that call these oceans home."
Expanding the marine park's boundaries was a positive step, WWF-Australia head of oceans Richard Leck said.
"And we're pleased to see an increase in sanctuary zones, including shelf protection to the north of the islands and deeper water habitats to the south and southeast of Heard Island," said Mr Leck.
"However, the new zoning plan fails to provide increased protection for most of the high conservation value areas identified in the government's own scientific review and an independent science review."
These critical foraging grounds would remain exposed to pressures like commercial fishing without increased protection, he said.
WWF-Australia has launched a petition calling on the government to significantly expand Heard and McDonald Islands Marine Reserve and increase protections from industries like fishing.
Consultation on the proposed marine reserve expansion started on Friday and closes on September 5.
The government said it was also progressing ratification of the High Seas Biodiversity Treaty.
Tabled in the parliament last week, the treaty will help establish marine protected areas on the high seas, which will complement Australia's own network of domestic marine parks.
