Chris Hipkins is criticising his party's former policy on pricing farm emissions.
Labour has released a pledge to review and reform the Emissions Trading Scheme - saying the price is too low.
It wants farmers to adopt new tech to reduce emissions, and isn't campaigning on making them pay for agricultural emissions, as it did for nearly two decades.
Hipkins says he's not convinced it would've worked.
"We went through that whole process, it actually would have been very difficult to pull it off. That was all done before I'd become the leader of the Labour party - I'd inherited that one."
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