Conservation group WWF says the Government is using misleading statistics to meet an international promise to protect the marine environment.
At the United Nations Convention on Biological Diversity conference in Japan, New Zealand reaffirmed an earlier promise to protect 10% of its marine area by the end of this year.
The Government reported more than 8% is already protected.
But the Worldwide Fund for Nature (WWF) says the true figure is less than 1% of New Zealand's waters.
Its marine campaigner, Bob Zuur, says the Government's figures only apply to the coastal areas out to 12 nautical miles from land, not the entire Exclusive Economic Zone.
The Conservation Minister has been unavailable for comment.