The Green Party wants to create one of New Zealand's largest marine sanctuaries off the South Taranaki coast to protect animals from seabed mining.
The sanctuary would be 50 times the size of Lake Taupō and the party said it would finalise the boundaries by working with iwi, communities, and the Department of Conservation.
If the sanctuary plan was successful, it would rival the proposed Kermadec Ocean Sanctuary, a new marine protected area in the exclusive economic zone.
That bill has passed its second reading, but it was delayed late last year when cross-party negotiations stalled.
Greens leader James Shaw said the sanctuary would protect blue whales and 37 other species of marine mammals in the area.
"National has been happy to sell off [the area] to the highest bidder to drill and mine.
"One hundred years ago, there were more than ten times the blue whales there than there are now. It's time to stop taking them for granted."
The Greens would also try to stop a permit granted to a company to dredge 50 million tonnes of sand a year from the South Taranaki Bight, Mr Shaw said.
"Iron sand seabed mining vacuums up the seabed, filters out minerals, and then dumps the mud back into the ocean.
"For the whales, it's like someone dumping the contents of a vacuum cleaner onto their dinner plates."
Mr Shaw was not worried a clamp down on seabed mining could lead to job losses.
"Oil and gas jobs are actually highly transferable, so there was a dip recently when the price of oil dropped, and a lot of the jobs in Taranaki actually moved to the central North Island to a lot of the geothermal operations."
He said if elected to government, current oil explorations would be allowed to continue until their permits ran out.