National MP Judith Collins has lashed out at Fonterra, saying the farming co-op is losing touch with its members.
Fonterra backs the Government's new push to clean up the country's waterways, announced on Thursday afternoon by Environment Minister David Parker.
"If we don't fix things now they only get worse and will be more expensive to fix," Parker said.
"Cleaning up polluted waterways is a long-term challenge that will take a generation to fix, but the steps in this plan will make a real difference and get things heading in the right direction."
Less than an hour later, Fonterra expressed its support on social media.
"We support the Government's freshwater goals and will support our farmers in achieving them," the country's largest company said on Twitter.
"Healthy freshwater is important to our country and integral to our strategy to create more value from our New Zealand milk."
Collins told The AM Show she's "worried" about Fonterra.
"They seem to be very intent on cosying up to Governments - their head office is in the Viaduct in Auckland, it's a very long way from the farmgate. They just need to think about their supply of farmers, what they're going through, their difficulty of getting finance, their difficulty of dealing with everything that they've got.
"They want clean waterways too, but they don't like this slapping them every single time there's an opportunity."
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She said farmers had already spent $1 billion fencing waterways off, and suggested efforts to make Kiwi rivers safe to swim in again were in vain.
"I used to swim in a river when I was a kid and there was great big fat Congo eels there, so I hope you like that."
Labour MP Willie Jackson, appearing alongside Collins on The AM Show, said a "lot of farmers" back the Government's efforts.
"We want to clean up the mess these guys created over nine years. We're looking at a generation, and farmers play a really important part in doing that," he said.
"I think that this is a Government who are surprising the National Party, because they didn't think one farmer would come on board."
He said the rivers are unswimmable because the previous National Government let farmers "do whatever they wanted to do", a claim Collins rejected.
"In which country in the world is dairy farming more sustainable, more ecologically sound than New Zealand? The answer is there is none."
National environment spokesperson Scott Simpson said the proposals would "smash the economic engine of our country".
Consultation on the proposed changes is open until October 5.