Another group that promotes improving water quality has resigned from the government's Land and Water Forum.
The Federated Mountain Clubs, which has 20,000 members, has written to the Environment Minister Nick Smith saying it is pulling out.
Forest & Bird said it was leaving the forum after its recommendations had been largely ignored by government, and Fish and Game said it was being muzzled and stopped from speaking out on environmental issues.
Federated Mountain Clubs vice-president Jan Finlayson said the freshwater policy was the breaking point.
"The government has treated Land and Water Forum very improperly. I think the stakeholders acted in good faith but were let done by a government that simply ignored their advice."
The Land and Water Forum gives more than 50 stakeholders, including industry groups, non-governmental organisations (NGOs), iwi, scientists and others a chance agree on recommendations to be made to government.
Green Party water spokesperson Catherine Delahunty said the number of groups leaving made a mockery of the forum, which she said was dissolving before her eyes.
"It just shows that the process is being undermined by the government. What was started with the best of intentions has now become no longer viable for the environment groups.
"If there's only one or two of [the environmental groups] left and the forum's bleeding these key leadership groups, then it's not longer a collaborative process."
Ms Delahunty said the government had been cherry-picking the forum's recommendations on freshwater management.
A spokesperson for Environment Minister Nick Smith believed the environmental groups were trying to score political points in an election year by resigning from the forum.
The spokesperson said the forum's work was largely done and if National was re-elected in September then the Minister would hope groups like the Federated Mountain Clubs reconsider their position.
But Ms Finlayson said there was nothing political in her group's move.
"We see that our colleagues in Forest and Bird and in Fish and Game have been treated very badly.
"We see no point in remaining in the plenary group."
The Federated Mountain Clubs hoped that its resignation from the forum would prompt a formal review of the way collaborative groups set up by the government were treated.
The government announced last month a goal to make more rivers swimmable but it would do so by weakening the threshold for what qualifies as the best quality waterway to swim in.
The policy has attracted widespread criticism, with the lobby group Choose Clean Water has put up a billboard in central Wellington slamming the policy and urging New Zealanders to protest to the Prime Minister.