Simon Bridges is backing claims by one of his MPs that ending oil and gas exploration is the "worst thing" for the climate.
The Government last week said with a few exceptions, no more permits for oil and gas exploration would be issued from now.
The ban doesn't affect existing permits, some of which run for another few decades, but the National Party believes jobs will start being lost right away.
"There is no question there will be jobs gone before the next election, alright? You mark my words... the investment's going to dry up."
Mr Bridges says he spoke to industry leaders last week, and they told him they won't be hiring new people as New Zealand tries to wean itself off fossil fuels.
"If you look at this, it just doesn't work at any level. It's a body blow for the regions, but more than that it's bad environmentally. It just doesn't work."
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That's because he thinks energy-hungry industries will turn to coal instead, as the gas dries up.
"I've been over it 100 times when I was Energy Minister. When you've got Fonterras, when you've got households that use the gas and you turn that off and there aren't viable alternatives, they move to coal - which is double the emissions."
According to the US Energy Information Administration, burning natural gas releases about 40 percent less carbon than coal and 25 percent less than gasoline. But drilling for it can release methane, which is around 30 times worse than carbon dioxide when it comes to warming the atmosphere.
If no new gas fields are found, New Zealand has about 11 years' gas supply left on current rates of usage.
Mr Bridges said he agrees that fossil fuels will have to go one day, but declined to put up a deadline of his own.