The Green Party says government officials are investigating the opening up of a fifth of Mount Aspiring National Park to potential mining.
The party on Tuesday released an excerpt from a document it says is being circulated by Government officials tasked with investigating the mining of parts of the conservation estate.
The document includes a recommendation by officials that the northeast section of the Mount Aspiring National Park - about 20% of the total area - be considered for removal from Schedule Four protection.
The Green Party co-leader Metiria Turei says that would be a serious attack on a major economic resource.
"They're talking about taking a fifth of that area, which is a vast resource in terms of the biodiversity the ecosystem services and fresh water - the tourism values."
Energy and Resources Minister Gerry Brownlee says no decisions have yet been made and accuses the Greens of scaremongering.
"What I would suggest to them is, if they are seriously concerned, take up some sort of a camping position high on Mt Aspiring and wait for the bulldozers. I think they'll be there a very long time."
But the Government says it is no secret it is doing a stocktake of mineral resources.
Straterra, a lobby group for the mining and energy sectors, says it makes sense for the Government and the public to have a full understanding of the country's mineral wealth.
Mr Brownlee says he expects to receive the report in the coming weeks.