The Greens want to ban koala habitats from being cleared to ensure the native marsupial survives.
The minor party hopes such a moratorium would block the Morrison government's decision to allow a controversial quarry extension in Port Stephens to go ahead.
Fifty-two hectares will be cleared to make way for it.
Greens environment spokeswoman Sarah Hanson-Young says the project will be a death warrant for the national treasure.
"Unless habitat clearing is stopped, koalas will soon be extinct," she said.
"Off the back of the worst bushfires in history which killed a third of NSW's koala population and destroyed millions of hectares of habitat across the country, no approvals for developments on koala land should be given."
The party will introduce to parliament a moratorium on habitat clearing.
Koalas are considered vulnerable but could be put on the endangered species list after last season's bushfires destroyed key habitats in NSW, Queensland and South Australia.
A NSW parliamentary report separately found koalas will become extinct before 2050 without urgent intervention.
After federal Environment Minister Sussan Ley announced approval for the quarry, her NSW counterpart Matt Kean appeared to back away from his own government's approval of the project.
He called on Ms Ley to closely consider her decision in light of the bushfires.
She said the company behind the project had promised to establish a 74 hectare koala habitat corridor - 22 hectares more than the venture would destroy.