Trade Negotiations Minister Tim Groser says that New Zealand would not agree to a carbon tax if it followed Prime Minister's John Key's suggestion of harmonising its climate change policies with Australia.

Speaking this weekend on TV3's "The Nation" he said: "This government will not replace the ETS with a carbon tax and I would be very surprised if our opposition had different views on that."

He said New Zealand's previous Labour Government had tried to model its emissions trading scheme on both the European ETS and Australia's original proposal which was very similar to ours.

"Then the Australian political debate matured, and Australia replaced it with a carbon tax, which is a totally different system," he said.

"However, the current plan is that we've changed into a trading scheme in 2015, so if that's the case then the possibility of doing what the Prime Minister has said is absolutely on the table."