The Government could lose as much as $8 billion in tax revenue by putting a stop to oil and gas permits around the country.
The figure is official advice from the Ministry of Business Innovation and Employment, covering tax royalties from 2027 to 2050.
The figures have been checked by Treasury, but not everyone agrees.
"They actually don't know what the number is because they're basing it on a possibility of what might be out there which they don't actually know," Green Party co-leader James Shaw says.
However, the Opposition is going on the attack over the figures.
"Eight billion and that's just the Crown royalties. So, in fact in terms of jobs, in terms of growth and profits, we're talking about tens and tens of billions that are lost to us," National Party leader Simon Bridges says.
New Zealand has 57 existing exploration and mining permits all of which will remain in place - some for up to 40 years.
Public and industry submissions are now being called for, with the bill banning future exploration expected to pass its first reading this week.