National says the Government has failed to provide evidence that axing oil and gas exploration will reduce carbon emissions.
Energy Minister Megan Woods told Newshub Nation on Saturday it was "common knowledge" and a "widely held" view, but didn't back it up with research.
"It's not an interpretation. It's a matter of fact," she told the show.
Advice from the Ministry of Business, Innovation and Employment (MBIE) said it would just force manufacturers to take production offshore, to countries where coal was still being dug up - like China.
- Drilling ban could cost NZ $8 billion over 23 years - MBIE
- Oil industry says it had no warning of ban
But National energy spokesperson Jonathan Young says the ban isn't going to reduce emissions.
"Companies like Methanex that rely on natural gas from New Zealand, if they can't get their supply and they can't supply the market, that will be produced in places like China, who use coal to produce methanol."
Ms Woods says China's cap-and-trade system means if it a New Zealand company started burning coal there, other production would have to "come offline".
Mr Young says it would still have three to four times the level of emissions as natural gas.
"I'm very cynical. I think it's just the Government trying to close down people's voice on this issue. It's probably the poorest form of Government I've seen for such a long time."
People were given only two weeks to have their say on changes to the Crown Minerals Act.
Mr Young says normally people are given three to six months to submit. He says natural gas provides 15 percent of New Zealand's electricity, and prices will go up if it runs out.
"The minister keeps saying the price of electricity is going to decrease, not increase. I just can't see how she's going to achieve that."
Ms Woods said MBIE's analysis failed to take into account the "rapid change" in technology happening around the world.
"It's not the first or last time that a minister won't agree with all the advice they receive. Let's remember, this is advice, not instruction."
Methanex uses about two-fifths of New Zealand's gas production. It has signed agreements to keep producing methanol in New Zealand until at least 2029.