National Leader Simon Bridges is criticising the Government for pushing out the timeframe in which it wants to bring farmers into the emissions trading scheme.
Before the election, both Labour and the Greens had policies to bring agricultural emissions into the scheme by 2020.
But the Government today said its plans were to start charging farmers by 2025.
Although Bridges called this a "backdown," he also said it would be unfair to bring farmers into the emissions trading scheme (ETS) before that time.
And he was also unsure as to whether farmers should be brought into the scheme after 2025.
He said National's policy on this issue was that farmers should only be brought into the scheme if the agricultural sector "met certain conditions".
These include increased productivity levels and "finding the science" to make continuous improvements.
"We think it's about partnership, rather than pricing; it's about technology not taxation. It's about on farm tools that would really make the difference, not some arbitrary timeline to get to putting agriculture into the ETS."
Earlier today, the Government's Interim Climate Change Commission (ICCC) recommended agriculture be brought into the ETS from 2025.
It would be at a 95 per cent discount rate, meaning farmers would only pay the cost of 5 per cent of their emissions.
The average cost on beef production was estimated at $0.01c per kg of beef, $0.03c per kg of sheep meat, and $0.04c per kg of venison.
Bridges said this was just another tax on farmers who were already some of the most emissions friendly in the world.
"To bring them in [to the ETS] and face a tax that other countries just don't face, means they will be uncompetitive."
He said that would hurt farmers and, in turn, would hurt the economy and everyday New Zealanders.
But Agriculture Minister Damien O'Connor said there were many farmers across New Zealand who were committed to do their part to reduce climate change.
"Are we asking too much [of farmers]? No I don't think so."
He said the price farmers would be asked to pay would not amount to an onerous burden on the sector to achieve "what will be a world-leading goal".
He said the benefits farmers would get from this would more than outweigh any of the downsides and short-term costs.
Speaking at a media conference unveiling the ICCC's report this morning, Climate Change Minister James Shaw said there had been a "remarkable shift" in the agriculture sector over the last few years.
"The sector itself is now saying that farm-level emissions pricing is part of the solution to reducing New Zealand's emissions from climate change."
He said that was a significant position and a level of consensus that had been reached between the sector and the Government that is "historic".