Plans for a long-debated coal mine in the NSW Bylong Valley have again been referred to an independent panel, this time for the final go-ahead.

The open-cut underground mine proposed by South Korean company Kepco Bylong Australia would be built near Bylong, 55 kilometres north-east of Mudgee.

The project is intended to operate for 25 years, extracting 6.5 million tonnes of run-of-mine coal per annum.

The NSW Department of Planning and Environment has completed its final assessment report and said the development is approvable, subject to stringent conditions.

The recommendation came just hours after the UN released a landmark report that warns of significant global climate consequences unless carbon emissions are cut to zero by 2050.

Carmel Flint from Lock the Gate Alliance said this mine is a step in the wrong direction.

"We think it is a really bad decision by the Planning Department," she said.

"It is underscored by the fact that we have had this dire warning from international scientists that we need to phase out fossil use.

"To be approving or recommending approval of a big new thermal coal mine in a greenfield area, we believe is completely at odds with that and isn't the direction we should be going at this point."

336 out of 364 community members opposed mine

The development application and environmental impact statement were placed on public exhibition in 2015 and received 364 submissions, of which 336 opposed the project.

It was referred to the then Planning Assessment Commission for a merit review, which raised concerns about the mine's heritage impacts on Tarwyn Park — a farm internationally recognised for its natural sequence farming methodologies.

The property was developed by environmental pioneer, Peter Andrews, but Kepco purchased it from the Andrews family in 2014 for more than $14 million.

Tarwyn Park was established by pioneer conservation farmer Peter Andrews, as an example of 'Natural Sequence Farming'. ( Tim Lamacraft )

Following advice from the state's Heritage Council, the department said it placed appropriate conditions on the development to protect the heritage of Tarwyn Park, including a prohibition on open-cut mining on the property.

Kepco Bylong Australia's chief operating officer Bill Vatovec said the company's revised mine plan would significantly reduce impacts on Tarwyn Park.

The project is expected to create up to 645 jobs during construction and 450 jobs during the peak operational phase.

Mid-Western Regional Council Mayor Des Kennedy said it would help the local economy prosper.

"We want to see the Kandos, Rylstone, Bylong, Mudgee, Gulgong towns grow with new families coming into the region, " he said.

The matter has been referred to the Independent Planning Commission which will hold a public hearing next month before making its final determination.

As the former Planning Assessment Commission has already held a public hearing in relation to the project, merit appeal rights in relation to any future determination by the renamed Independent Planning Commission have been extinguished.