Trade Minister Tim Groser is misleading the public over the terms of the Trans-Pacific Partnership (TPP) free trade agreement the Government is negotiating, the Green Party says.
Mr Groser has rejected Opposition party complaints about the agreement since a leaked document appeared to confirm states signing up to it could be sued by foreign companies over laws they consider are contrary to their interests or will cost them money.
He gave an assurance on Thursday he wouldn't sign anything that compromised New Zealand's sovereignty and said the Government's legitimate right to regulate and pass laws protecting the environment would be protected.
Greens co-leader Russel Norman says the catch is in the word legitimate.
"Who decides what is legitimate? If a case is brought, it will be an international tribunal deciding that, not the Government," he said on Friday.
Dr Norman told Radio New Zealand the tribunal would ultimately decide what the Government could or could not do.
He says tobacco companies would be able to sue over regulations forcing them to sell cigarettes in plain packets, and oil companies over rules around drilling which would be costly to comply with.
Mr Groser has told Parliament the TPP negotiations still have a long way to go.
"No decisions have been made, no documents have been put to ministers, this is just another beat-up," he said.
The TPP is an extension of a free trade agreement between New Zealand, Brunei, Chile and Singapore which has existed since 2006.
Countries negotiating to join it are Australia, Malaysia, Peru, Japan, the United States and Vietnam.
The talks started four years ago and the next round starts in San Diego on July 2.
AP