The report, which was conducted by Shenhua's environmental consultant Dr Steve Phillips, suggests the species may be locally extinct "even before the mine commences".

According to the report, which was discussed by the mine's technical working group at a meeting in March, a survey conducted in 2012-13 noted a koala density of 0.3 koalas per hectare on the site in the NSW Liverpool Plains.

However, a study done this year indicates the density has shrunk to 0.04 per cent per hectare.

"What that represents is a population decline of 87 per cent," the report stated.

"On that trajectory and worst-case scenario, it indicates that the koala is heading to localised extinction even before the mine commences."

The report's release comes as the company prepares to finalise its environmental management plans for state government approval.

A NSW Department of Planning, Industry and Environment spokesperson said a koala plan of management would make up a vital part of the company's environmental management plans.

"The Watermark Coal Mine was approved by the Independent Planning Assessment Commission in 2015 following a comprehensive assessment and consultation process," the spokesperson said.

After consulting with the koala technical working group in coming weeks Shenhau is expected to submit its final koala plan of management.

"The final plan will be carefully reviewed to ensure all conditions of approval are met, including maintaining 1200 hectares of koala habitat on the site, establishing new koala habitat corridors, and rehabilitating the mine to create additional koala habitat in the longer term," the spokesperson said.

"The mine will be developed progressively over 30 years, enabling the retention of areas of koala habitat in and around the site to support local koala populations.

"The implementation of the koala plan of management will be monitored by the koala technical working group and strictly enforced by the department's compliance unit."

In the wake of the report Lock the Gate Alliance spokeswoman Georgina Woods, has called on the state government to revoke Shenhua's permission to clear koala habitat.

"Given what has occurred across the rest of NSW, we believe every effort must be made to stop their [koalas] localised extinction on the Liverpool Plains, beginning with revocation of the Watermark coal mine development consent," Ms Woods said.

Shenhua declined to comment.