Federated Farmers president Katie Milne in front of Michael Spaans, Bruce Wills, Mike Petersen, Carolyn Mortland (Fonterra), John Loughlin and James Parsons at the Ngaruroro River in Hawke's Bay on Tuesday.

Farming leaders representing 80 per cent of the industry have pledged to make all New Zealand rivers swimmable, although they don't say how or by when.

Confessing that not all rivers were in the condition they wanted them to be, and that farming had not always got it right, the group said the vow was "simply the right thing to do".

Launching the pledge by the banks of the Ngaruroro River in Hawke's Bay, spokeswoman for the group and Federated Farmers president Katie Milne said the intent behind the commitment was clear.

Farming leaders describe their goal of making all rivers swimmable "ambitious".

"Many of our rivers are not in the condition we all want them to be. We are doing this because we want our kids and their kids to be able to swim in the same rivers that we did as children. And by swim we mean swim. It's as simple as that."

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The move was welcomed by Labour primary industry spokesman Damien O'Connor who said he had been telling farming groups for the last 12 months they needed to say something "to be on the same page as the public who have a desire for swimmable rivers".

"It's a great first step. (National minister) Nick Smith's attempt to appease the farming sector by dumbing down the standards helped neither the environment nor the farmers. This will help them build their social licence to operate," O'Connor said.

Green spokeswoman for the environment, Eugenie Sage, said the statement was no surprise, but it had to be made meaningful by concrete commitments.

"It needs to be backed up by measures such as stronger regulatory controls on pollution, lower dairy cow numbers to reduce nutrient pollution, ending PKE use, winding up Government subsidies for big irrigation schemes which encourage intensification, reducing dairy sector debt; and shifting to more sustainable farming models."

Milne conceded farming had not always "got it right" in recent years, but progress had been made, there was more to be done, and it had to be done fast. She defended the lack of specifics in the pledge.

"Today isn't about laying out the detail on the huge amount of work going on already on farms up and down the country and how these efforts will need to increase."

"It's about us as farming leaders signalling our commitment to making New Zealand's rivers swimmable and doing everything we can to achieve that," Milne said.

There was no timeline on the commitment because each community would need to decide that for themselves.

"We know that we have work to do. We know it will be challenging for farmers. We know the answers are complex and we don't have them all now. This commitment is simply the right thing to do in playing our part to give back to future generations what we enjoyed as kids," Milne said.

Primary Industries Minister Nathan Guy and Environment Minister Dr Nick Smith welcomed the initiative.

They said the new national policy statement on freshwater management was announced on August 9 and introduced a new requirement for rivers to be suitable for swimming. It sets a timetable of 90 per cent of rivers and lakes to be swimmable by 2040, establishing a system for monitoring and reporting and requires each of the 16 regional councils to set regional targets by 2018.

Tourism Industry Aotearoa said, while some positive steps had been taken recently, it did not believe they went far enough.

It said that, post the election, it wanted to see the freshwater standards revised.

Greenpeace welcomed the acknowledgement that the problem with waterways was greater than previously admitted.

Agricultural campaigner Gen Toop said without a plan to back it up, the pledge could be seen as fairly meaningless.

She recommended the farming leaders adopt the Freshwater Rescue Plan signed by 16 organisations and experts. The plan calls for a cut in cow numbers, and an end to the $480 million crown irrigation fund.

The farming leaders group which launched the pledge is an informal grouping of pastoral farming leaders that was established in May this year.

The current membership is Mike Petersen (governmental agricultural trade envoy), Michael Spaans (dairy farmer and DairyNZ chairman), James Parsons (sheep and beef farmer and Beef + LambNZ chairman), John Loughlin (Meat Industry Association chairman), Katie Milne, Bruce Wills (former Feds president Ravensdown director), and John Wilson (dairy farmer and Fonterra chairman).