The Government is threatening to intervene if regional councils do not take more action to stop farmers putting effluent in waterways.
The eighth annual review of the Clean Streams Accord shows the proportion of farms breaching their resource consents has increased again to 16%.
In Canterbury, serious effluent breaches have more than halved, but non-compliance in Northland is still about one-quarter of all farms.
In Waikato, serious effluent breaches have leapt to 27%.
Agriculture Minister David Carter says the Government won't stand by and let councils shirk their responsibilities.
He says Canterbury has significantly improved its performance since commissioners were appointed last year.
Local Government New Zealand spokesperson Fran Wilde says most councils are improving and the few that are not will be aware of the problem.
Industry body Dairy New Zealand says industry initiatives are lifting the compliance rates and it is confident that will be reflected in the next progress report.
The current report covers the 2009-10 dairy season.
Federated Farmers dairy chair Lachlan McKenzie says the averaging out process used to compile the national figures is painting a distorted picture of compliance rates.
He says in Taranaki, where there are annual inspections of all dairy farms, the compliance rate is almost 100%.
