The Green Party has criticised an agreement between Rotorua farmers and the regional council to reduce nitrogen levels in Lake Rotorua saying the compromise further erodes the country's clean green image.
On Monday, representatives of the Bay of Plenty Regional Council, Federated Farmers and the Lake Rotorua Primary Producers' Collective signed a memorandum of understanding - known as the Oturoa Agreement - to significantly reduce nitrate levels in the lake during the next 20 years.
The agreement bought to an end a two-year Environment Court battle between Federated Farmers and the regional council after the council introduced a regulation requiring the annual nitrogen load going into the lake had to be slashed by more than 300 tonnes within 10 years.
Federated Farmers said it would withdraw its appeal after agreeing to a compromise which would see 70 per cent of the original target reached by deadline, with the remainder by 2032.
Green Party environment spokeswoman Eugenie Sage said 20 years was too long to wait to cut nutrient loadings in the lake.
"The proposed timeframe to meet the nutrient reduction target is too long," she said.
"We need clean water rules and stronger land use controls now, not just for Lake Rotorua but across New Zealand.
"Without stronger national rules to protect our lakes, rivers and streams we will continue to see our clean green image eroded, threatening our agricultural exports."
Ms Sage said voluntary agreements were not enough to clean up waterways.
"Dairy cows continue to access and pollute rivers and streams despite a decade of Fonterra's voluntary Clean Streams Accord. A 2011 MAF survey found almost half of Bay of Plenty dairy farms had waterways from which stock were not excluded."
Ms Sage said for water quality to improve the country needed national environmental standards to protect waterways from stock access, limit stock numbers in sensitive catchments and set measurable limits on nitrates and other contaminants.
"If councils then want to set stronger standards through their plans they can.
"Without strong national policies and standards, the threat of court action will see regional councils caving in to land users with long timeframes and weak plan provisions," she said.
However, Rotorua and Taupo Federated Farmers provincial president Neil Heather, said Ms Sage was completely missing the point.
"Humans have lived around the lake for nigh on a thousand years," Mr Heather said.
"While you can't turn that around at the click of your fingers, the hard work of farmers on advice from the likes of DairyNZ, councils and of course, the community, has paid off.
"A few years ago we were told improvements in Lake Rotorua would take decades and it would get worse before it got better.
"But by working as a community and ignoring the 'doubting Thomases' we achieved a water quality target experts thought would take decades.
"A Lake Rotorua Trophic Index Level of 4.2 was the objective, but last year it came in at 4.1.
"That was no fluke but part of an improving trend."
Mr Heather said the agreement was the next step forward for the lake and deserved to be held up as a national example.
"It is community team work and means the Greens have to decide if they are going to be part of the solution or part of the problem," he said.