Norwegian oil firm Statoil has been granted a permit to explore a further 1670sq km of seabed off Northland's west coast.
The new block adjoins a 9800sq km area in the Reinga Basin, about 100km off Ninety Mile Beach, that the state-owned oil giant is already exploring. The two areas will be explored together.
Statoil's expanded area is one of 15 new oil and gas exploration permits announced by Energy and Resources Minister Simon Bridges as part of Block Offer 2014. It is the only new permit in Northland.
The news, which comes just days after the Stopstatoil Festival at Ahipara, has been welcomed by Northland MP Mike Sabin but decried by environmental groups.
Mr Sabin said the Northland-Reinga basin totalled 54,000sq km and was one of the country's most promising frontier basins.
Oil was already the country's fourth largest export earner with a value last year of $1.7 billion. The Government received about $800 million each year, money which could be invested in infrastructure such as schools, roads and hospitals, Mr Sabin said.
Combined with the development of onshore minerals, it could provide a "circuit-breaker" for the Northland economy.
Forest and Bird said the new permits were another sign the Government was failing in its duty to protect New Zealand against the worst effects of climate change.
The deep-sea exploration permits reportedly included part of the Maui's dolphin sanctuary, while one of the onshore permits covered part of Victoria Conservation Park in Taranaki. Advocacy manager Kevin Hackwell said Forest and Bird was concerned the petroleum industry was being allowed to buy the rights to drill or frack in such areas.
"But all New Zealanders should be concerned about new oil drilling and fracking wherever it might occur, given the huge dangers of climate change caused by the burning of fossil fuels."
A report released yesterday by Climate Action Network Europe had given New Zealand a ranking of 43 out of 58 countries for its poor record on climate change.
Paal Haremo, Statoil's vice-president of exploration, said the company would continue to engage with local communities and other stakeholders, "to listen and learn, and inform about our plans".
The company appointed Bryn Klove as its country manager for New Zealand last week. He will head Statoil's Wellington office.
Seismic surveying is already under way in the Reinga Basin. If results are promising the first test wells could be drilled in 2020.