A fishing lobby group says regulators would be guilty of double standards if they let a protected area of seabed be mined while refusing to allow bottom-trawling.
Chatham Rock Phosphate last week lodged an application for marine consent to mine 820 square kilometres of the Chatham Rise over 30 years.
Part of the rise is a benthic protection area, which means it cannot be trawled or dredged.
The company says fisheries will not be affected by the mining, but chief executive of the Deepwater Group, George Clement, rejects that.
"There is a concern that there's some double standards there because while it's protected from the effects of trawling, and we don't fish in there so it's a pristine area, the mining that's proposed there would completely devastate it - trash the whole place."
However, Chatham Rock Phosphate says it has assessed the potential environmental impact of mining for phosphate in the area and can show how it will minimise any effect.