Forest & Bird said smoke can be seen rising from several cracks on the plateau, above a historic mine shaft. Bathurst Resources has recently drilled core samples close by, and drained a lake in the vicinity.

The coal seam that Bathurst recently won permission to open-cast mine on the plateau is adjacent to the seam that is currently being mined at Bathurst’s Cascade Mine, in a valley below the Denniston Plateau, Forest & Bird field officer Debs Martin said.

“This is too much of a coincidence. There’s little doubt this is linked to Bathurst’s mining activities,” she said.

“All efforts should now go into stopping the whole coal seam from catching alight. A major underground fire could seriously affect the unique trees and wildlife beyond the area that Bathurst has permission to mine.”

Forest & Bird staff have visited the site, and alerted DOC to the situation, as the Denniston Plateau is public conservation land.

“To our knowledge, Bathurst has not made any public statement on this issue – which is surprising, given the serious implications of an underground coal fire,” Martin said.

Calls to stop Bathurst Resources from mining at Denniston Plateau are ill-informed, NZ conservation minister Nick Smith said.

“The smoke is coming from an old mine shaft where low level underground fires have burned for decades,” he said.

“These fires also occur naturally in this rich coal field. These smouldering seams pose no significant threat and are left to burn naturally. Smoke appears periodically relative to atmospheric conditions and has done so for many years.

“It is ridiculous for Forest & Bird to blame Bathurst for these fires and to demand any work stop before they are put out. The smoke is some kilometres from Bathurst's escarpment mine. Forest & Bird should check with the department and be better informed before making these sorts of public claims.

“This smoke from an old mine shaft just highlights the degree to which the Denniston Plateau has been previously mined and that it is not the pristine area that some claimed. It reinforces the government's decision to allow the Denniston mine to proceed.”

ICN put in a request to Bathurst Resources to answer the claims but had not received a reply by publication time.

On Bathurst Resources’ website it defends its environmental record.

“Bathurst’s environmental management plans cover a wide area and involve significant expenditure,” it said.

“For example, the company has made a commitment to protecting the great spotted kiwi through predator control over 500 hectares of the Heaphy Track for 35 years.

“The company has worked with the Department of Conservation to determine how it can achieve a net gain to the conservation estate.

“The Department identified the Heaphy River as a unique eco-heritage area that would benefit from Bathurst’s support.

“Bathurst will use modern mining techniques to minimise environmental effects while also restoring and enhancing the local environment over the long term.

“Protecting New Zealand’s conservation estate and unique biodiversity is something we all care about deeply, but government resources are limited.

“Bathurst is working with the Department of Conservation to ensure wealth generated from the coal can be used to deliver environmental benefits that exceed impacts.”