Ironsands Offshore Mining Ltd has been given a five-year permit to explore for seabed minerals across 220sq km off the New Plymouth coastline.
The permit was granted on May 8 by the Ministry of Business, Innovation and Employment's New Zealand Petroleum and Minerals. It lasts five years, and will allow exploratory drilling.
The area overlaps one end of the large West Coast North Island Marine Mammal Sanctuary, which was created in 2008. It was made specifically to protect critically endangered Māui dolphins.
There are 55 to 75 of the dolphins left alive in the wild, Radio New Zealand reported.
Greenpeace and the Ngāti Ruanui iwi are shocked and outraged by the approval.