A Taranaki dairy farmer has been fined $66,000 dollars for allowing his stock effluent disposal pump to leak into a stream.

Francis John Mullan, of Opunake, was charged with allowing a poorly maintained pump at his milking shed to leak into the Oanui stream and groundwater.

Mullan owns eight dairy farms in the area and already has two previous convictions for similar offences. The $66,000 Environment Court fine is the largest ever for a farmer in the Taranaki region.

Meanwhile, the Central Hawke's Bay District Council has been formally told to stop dumping pollutants into the Tukituki River.

Its wastewater plants have breached their resource consent six times since October by discharging phosphates into the water.

Last week, the council blamed a failure with filters and said it would be fixed but could take at least three months.

Abatement notices have been served by the Hawke's Bay Regional Council, telling it to get on with the job.

It said the notices applied to treatment plants in both Waipukurau and Waipawa and clearly set out what needed to be done and the timeframe required.