"While US objectives are abundantly clear, New Zealand's response is not," he said.
"If New Zealanders are to be assured of a continued right to know about the presence of genetically organisms in their food, then a clear commitment is required from potential future governments that negotiators will have no mandate to'trade away' GM regulatory protections."
New Zealand and Australia have mandatory labelling regimes for GM food.
New Zealand also allows commercial production of GM crops but there have been no applications.
One of the diplomatic cables from the US embassy in Wellington and leaked by Wikileaks about a year ago, quoted New Zealand's top TPP negotiator, Mark Sinclair, as citing New Zealand's genetically modified organisms regulations as being among the issues that could be an impediment to concluding an agreement.
The US cable noted Mr Sinclair had said foreign investment was always open to populist views in New Zealand.
On the campaign trail today, Prime Minister John Key said he "wouldn't have thought'' New Zealand's current regime for GM was up for negotiation as part of the TPP talks.
"We've got a well established process when it comes to GM. Applications have to go through the Environment Protection Authority. As far as I'm concerned that's not changing."