Forest and Bird says Northland Regional Council and Fonterra are failing to protect Northland from dirty dairying.
Figures released this week show that this milking season more than 20% of dairy farms in the region have significantly breached resource consents.
Forest and Bird advocacy manager Kevin Hackwell says there are fewer than 1000 dairy farms in Northland and more than 200 of those are not complying with the rules.
However Northland Regional Council says the region's farmers deserve qualified praise as last season about 30% were offending.
The council's operations manager, Tony Phipps, says Northland farmers have invested heavily in improvements to effluent disposal systems and the region is beginning to see the results.
He says Northland has higher resource consent breach figures than other regions because the council's testing regime is more robust.
He says Northland's council, unlike some other regional councils, does not warn farmers before arriving to inspect their farms.