The Green Party is alarmed about new tenders for platinum exploration involving nearly 400,000 hectares in the South Island.
The tenders include more than 1100 square km on the West Coast as well as another 2600 square km in the Tasman area and 300 square km in Southland.
World Heritage sites and Schedule 4 land are excluded.
But Greens mining spokesperson Catherine Delahunty says the tenders involve areas with high conservation and recreational values.
In the tender document, the Ministry of Business, Innovation & Employment says companies submitting tenders must operate in an environmentally responsible way.
But Ms Delahunty says platinum extraction is extremely toxic and would involve new roads and dumping sites, in areas previously protected from logging.
Forest and Bird says it believes the public will oppose any bid to explore for platinum and gold in conservation areas in Westland and the Tasman region.
Forest and Bird spokesperson Kevin Hackwell says the area includes part of the Mohikinui River where conservationists have already fought a dam proposal, as well as areas around the Pelorus and Buller Rivers.
He says many people believe mining offers jobs and income in areas needing both, but they forget the high costs of mining include the production of toxic by-products.
Mr Hackwell says conservation land also produces income from visitors as well as recreational opportunities, and people will rally to protect such land.
In a statement, Conservation Minister Nick Smith says the process is at an early stage, and none of the prospecting would be on Schedule 4 conservation land.
Dr Smith says we need to know what is on the land so there can be an informed debate about whether permission to mine platinum should be granted.
Platinum New Zealand 2013 tenders opened on Friday. Tenders must submitted by April next year and exploration permits are expected to be granted in December 2014 for an initial period of five years.