The Department of Conservation is playing down reports of an underground coal fire on the Denniston Plateau, near Westport.
Forest and Bird released details today, along with a photo, of what it describes as coal fires on the plateau with smoke wafting out of historic mine workings on DoC land.
But DoC Buller area manager Bob Dickson said the fire "has been burning there for many, many, many years - decades, in fact".
"It's benign, it periodically emerges depending upon air pressure and wind shifts, and it poses absolutely no risk to the mining operations or indeed the wider Denniston Plateau.
Mr Dickson said the fires were outside the escarpment area of Bathurst Resources' mine development and there is no link between the fires and recent mining.
Conservation Minister Nick Smith said he was disappointed with Forest and Bird for what he said was misinforming the public about the fires.
The organisation was trying stop the mine's development, he said.
"They've had 10 goes in the courts at trying to stop this mine proceeding and they're really quite desperate and using the historic smoking as some sort of an excuse to relitigate that debate."