Winston Peters has told farmers NZ First won't support Labour's proposals to widen taxes and bring agriculture into the Emissions Trading Scheme.

The New Zealand First leader told more than 100 farmers in Ashburton that a water tax policy "won't work".

Labour intends introducing a water tax, which farmers fiercely oppose.

It also has a policy to bring agriculture into the ETS, meaning farmers would have to pay for pollution.

Mr Peters said NZ First wouldn't support that either.

Mr Peters told the Federated Farmers meeting in Ashburton on Wednesday that a water tax of two cents a litre - Labour is thinking about one or two cents a litre - would cost the average irrigated farm in Canterbury $29,000 a year.

"The stakes are high because $60 billion is tied up in agricultural debt," he said.

It seems Mr Peters is sending the same message to both parties on his water tax stance, although National has said it won't bring in any new taxes if it wins the election.

"Both parties are getting the same message, we think you are the devil in the deep blue sea with this policy and we are opposing both of you on this matter," he said.

"Labour and National envisage the same sort of cost structure against rural regional New Zealand when it comes to water."

Mr Peters said his party's survival depended on it keeping its word after the election.

"We've been around 24 years and we'll be around another 24 by keeping our word."

Meanwhile, Mr Peters did state that he would like to see exported bottled water taxed.

"We were the ones that announced that any water bottled offshore should attract a royalty, and go to the region whence the water came to help pay for the infrastructure of the region," he said.