Hundreds of timber industry job losses could be offset with $45 million in government and private investment into a new national park in eastern Victoria, The Wilderness Society says.

The 500,000 hectares of forest, east of Melbourne, is home to the critically endangered Leadbeater's Possum, but also provides timber for Australia's largest hardwood processor at Heyfield.

The timber mill's owner, Australian Sustainable Hardwoods, has threatened to shut down, with the loss of 250 jobs, without secure long term log supply.

The Wilderness Society commissioned consultants Nous Group to analyse the economic benefits of the proposed Great Forest National Park, which would include the towns of Healesville, Kinglake and Marysville.

It shows the national park could provide a $71.1 million economic boost annually and attract an extra 379,000 local and international tourists.

Those figures rely on a $45.2 million investment in better management and infrastructure, including the Healesville to Eildon hiking trail, a tree top walk and an eco-lodge.

The Wilderness Society's Victorian campaign manager Amelia Young said 760 ongoing jobs could be created, making up for the loss of "370 jobs directly in native forest logging".

"If the industry continues to log in these forests they are going to continue to be confronted with the controversy around their supply chain because [the] mountain ash system is at risk of collapse," she said.

"This timber mill is milling and processing an endangered species of timber."

The forest is home to the critically endangered Leadbeater's Possum. ( AAP: Healesville Sanctuary )

She said the jobs could be created in a range of areas to manage the forest and support tourism.

"If the park is being managed properly there will be a lot of jobs in managing pests and weeds, which are a huge problem, and also in managing the ecosystem services.

"These are people [timber industry workers] who work in these forests, they have the machinery, they have the expertise and they have the skills. What we need to do is transition them onto a sustainable footing so that they can have jobs for the long term that are supported by all Victorians."

Proposal will 'spell disaster' for timber mills, forestry group says

The State Government established the Forest Industry Taskforce to consider the region's economic and environmental future, including that of the Leadbeater's Possum.

But Tim Johnston from the Victorian Association of Forestry Industries said the proposal would spell disaster for timber mills in the region, and cost thousands of jobs.

"The industry wouldn't be viable if the Great Forest National Park, as proposed, was to get up," he said.

"The proposal would have extreme and disastrous impacts for the mill at Hayfield, but also for a number of other small family owned mills throughout the Yarra Ranges and beyond."

The Great Forest National Park would include the Yarra Ranges, Kinglake, Lake Eildon and Baw Baw national parks.