Government officials are warning the move to halt new offshore oil exploration permits could cost the country billions.
Energy Minister Megan Woods introduced legislation to Parliament today bringing the decision a step closer to being enacted and released new advice from officials at the Ministry of Business, Innovation and Employment (MBIE).
The ministry analysis estimated a cost to New Zealand of $7.9 billion in lost tax revenue between 2027 and 2050, but noted that would depend on future oil prices and interest rates.
Officials also warned of "broader economic impacts" to the national and Taranaki economy.
However, Ms Woods contested MBIE's estimates.
In a statement, she said those numbers were based on a GNS report which expressed caution about relying on resource estimates.
The GNS report itself noted "this study attempts to quantify what is almost unquantifiable", she said.
The ministry advice also cautioned that the ban could potentially increase global greenhouse emissions.
"The transfer of production to other countries that have higher emissions footprints may result in an increase in global greenhouse gas emissions, although the timing and scale of this impact are uncertain," officials said.
The legislation will go through a shortened four-week select committee process to ensure the block offer can get underway in early 2019.
Prime Minister Jacinda Ardern made the announcement in April to limit all future offers to onshore Taranaki as part of a 30-year plan to transition away from a reliance on fossil fuels.
"All existing permits are protected and will be allowed to run their full course - meaning we have many years' worth of gas supply remaining and exploration will continue," Ms Wood said.
"The long term picture is this: the world is changing. Climate change is happening and the world is racing to adapt and to stop its most damaging effects.
"We can't expect to rely on fossil fuels for our jobs and prosperity forever. The world is moving away from them and we have to be ready. That's why we are planning for the transition now to ensure we are creating jobs in new industries and in new forms of energy."
Environmental lobby group Greenpeace has congratulated the government for the move, but lashed out at MBIE, describing it as the "Ministry of Oil".
"They're essentially operating as the 'enemy within' by working with the oil industry to stop progress on climate change," Greenpeace executive director Russel Norman said.
"MBIE hasn't considered the economic and human consequences of climate catastrophe in their benefits and costs analysis - just like the oil industry they serve.
"Millions will die and whole cities will be flooded by climate change, but MBIE does not even consider these human and economic costs."
Greenpeace wants the government to go much further and cancel all existing exploration permits held by oil and gas companies.
National's Energy and Resources spokesperson Jonathan Young said the official advice proved how "arrogant and reckless" the government's decision was.
"This is an appalling decision made with no consultation or investigation into the real impact it would have. Now we know even the government's own advisors say it's going to cost New Zealand dearly and the government is going to try and ram the legislation through to avoid the necessary scrutiny.
"The government must own the mistake, admit to New Zealanders it got it badly wrong and reverse its decision."