Mt Te Kuha, looking towards Westport in the Buller region of the South Island's West Coast.

A new open-cast coal mine on the South Island's West Coast has been granted resource consent, but critics say the project will push endangered species closer to extinction.

Rangitira Developments Ltd, which includes Stevenson Mining, holds the mining permit for the ridge on Mt Te Kuha, about 12 kilometres from Westport.

The open-cast coal mine will cover 144 hectares, including 12ha of conservation land, 100ha of the Westport Water Conservation Reserve and the remainder on private land.

NEIL SILVERWOOD/SUPPLIED The proposed mine site at Mt Te Kuha on the West Coast.

Buller District Council Mayor Garry Howard said it was critical the Department of Conservation now approved the access agreement for the company to use the conservation land.

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"It is still in the hands of Government at this present stage. I'm very much aware that the last government had all but signed off the access agreement so I'm hoping that this won't be impeded by the the change of government."

Howard said the mine was "part of a mix" of jobs the area needed.

"We certainly see a place for high quality coal mining with very good environmental resource consent conditions."

In the company's application, Stevenson Mining chief operating officer Anne Brewster said the mine would create about 58 jobs.

"The plan of having day-shift operations only at Te Kuha will mean employees will have to reside in the Buller District, which is beneficial to the local community," she submitted.

The West Coast Regional Council granted the project resource consent on Tuesday, following a nine-day hearing before a three-person panel in September to help the various parties develop consent conditions together.

Regional council chief executive Mike Meehan said the council had undertaken an "extremely robust process" involving various experts, which assisted with the commissioners' final decision.

The hearing process ensured the "very best outcomes for the community, the environment and business are achieved".

The panel considered the effects the new mine would have on groundwater and hydrology, water quality, aquatic ecology, geotechnical issues, dust, the Westport water supply and climate change.

"The imposed conditions are robust and thorough and subject to input from all parties," Meehan said.

"They allow for adaptive management techniques to be undertaken in order to address any potential impacts that may arise."

Critics of the project warned it could push endangered species such as the South Island fernbird and West Coast green gecko closer to extinction.

Forest & Bird chief executive Kevin Hague said it was "horrifying that land held for conservation could be dug up for a mine in the 21st century".

"Everybody agrees that this area has high ecological values. It's one of our forgotten places – home to the largest population of our rarest butterfly, but languishing in the lowest category of conservation land," he said in a statement.

The organisation had 15 working days to lodge an appeal with the Environment Court.

Prime Minister Jacinda Ardern said earlier this month there would be "no new mines on conservation land".

Minister of Conservation Eugenie Sage said the policy related to new mines, so existing mines and applications like the one for the Te Kuha project would not be affected.

"The mechanism by which we implement policy is being developed and obviously taking advice and heard very clearly, [is] the need for clear guidance on applications that had already been lodged," she said.

"We determine applications under the current law."

A spokeswoman for Sage said she would not comment on the Te Kuha project at this stage.