The study, commissioned by the World Wide Fund for Nature Australia, reported an overall 71 per cent fall in the koala population across six firegrounds, from south of Port Macquarie on NSW's mid-north coast to near Ballina in the state's north.

Four major blazes had swept through the study areas last summer - a NSW bushfire season in which 25 people died and more than 5.5 million hectares were destroyed.

"That's why it's so important that national environment laws are strengthened to protect koalas and all threatened species," WWF Australia chief Dermot O'Gorman said in a statement.

"The Australian bushfires showed the world a future nobody wants ... koala numbers may not recover before another blaze sweeps through the east coast, causing localised extinctions."

The report found koala population declines at the six sites varied from around one third to a likely 100 per cent loss at Kiwarrak, south of Taree. Koalas were up to five times more likely to survive in areas where forest canopies were unburnt or partially burnt.

Authorities were encouraged to halt logging and other disturbances to unburnt forest canopies in northern NSW until after further koala population assessments.

Dr Stephen Phillips, a koala ecologist at report researchers Biolink, said the success of koala population recovery depended on the severity of population loss, management and conservation efforts, and sufficient recovery time.

"We need to wrap them in cotton wool," Dr Phillips said in a statement.

The report comes after at least two NSW Nationals MPs threatened to move to the crossbench if koala protection regulations in the state are not altered.

Chris Gulaptis, the MP for Clarence, has demanded the government review the Koala Habitat Protection State Environmental Planning Policy, which came into effect in March.

The policy simplifies the process by which koala habitats are recognised and protected, and extends the number of protected tree species from 10 to up to 65.

Both Mr Gulaptis and Coffs Harbour MP Gurmesh Singh last week argued the policy would damage regional communities and complicate farmers' work.

A NSW parliamentary inquiry found in July that koalas would lose their habitat and become extinct in the state before 2050 unless the government intervened.

It also found the current estimate of 36,000 koalas living in the NSW wild was outdated.

Australian Associated Press