Regional councils are letting dairy farmers get away with breaking their own rules, according to a report just released by Forest and Bird.
The group found that between July 2016 and June 2017, there were 425 cases of serious non-compliance. But despite this, some councils did not take any formal enforcement action such as an infringement notice, an abatement notice or prosecution.
Forest and Bird has compiled official information gathered from all the councils over the 12-month period to illustrate the state of monitoring and enforcement on the dairy sector across the country.
The group said some regional councils were failing even the basics of managing the significant environmental risks posed by dairy effluent.
Of the hundreds of cases of non-compliance, for 29 farms this was the third year they were seriously non-compliant. In one case, a Northland farm received four abatement notices and eight infringements notices but was not prosecuted.
A serious non-compliance means that an environmentally damaging activity has either occurred or was likely to occur due to poor practice.
Forest and Bird's freshwater advocate Annabeth Cohen said the lack of enforcement means more pollution was getting into rivers and lakes.
"Too many councils are letting farmers get away with breaking the rules and it's completely unacceptable."
Ms Cohen said dairy effluent could have serious consequences for the environment and her organisation requested the case notes from councils on the non-compliance issued.
According to the report, discharge to land was the largest single category. In instances where discharges were made on 'land', or 'land and water', there could be ponding of effluent on the surface of the soil, which Forest and Bird said could potentially have contaminated the groundwater.
In at least 16 per cent of all serious non-compliance, dairy effluent ponded on land.
Ms Cohen said there were significant inconsistencies and gaps in how regional councils were enforcing the rules around dairy effluent management.
Marie Brown is the policy lead at consultants the Catalyst Group, she has more than a decade of experience in compliance monitoring and enforcement.
She said he thought the report was useful in shining a light on an issue which was front of mind for the public.
"It's really important that councils are open to this kind of analysis and that where there are legitimate critiques, that they take them on the chin."
Dr Brown said there needed to be improvement on the way monitoring and enforcement was reported.
The report gave a score card to the regional councils. Waikato, which has the most dairy farms in the country, received an F.
The council has called the report misleading - although it admits it did provide Forest and Bird with some incorrect data.
The council's resource use director, Chris McLay, said it was very active at monitoring farms and took serious action, and that it was targeting high-risk farms this year.
"That means we won't get around all the properties in the region because many farmers are complying and they don't need to be visited every year, but what we will do, where we find non-compliance, we follow it up, we will be taking enforcement actions."
Ms Cohen said no one was holding the regional councils to account and they need to be reined in.
Earlier this year, Environment Minister David Parker announced $3 million for a unit which would oversee how councils manage consents.
Mr Parker said the unit was being introduced because monitoring and enforcement was variable across the country.
Details of the unit are still being decided.