The New Plymouth District Council's investment in its sewerage system has been questioned following four incidents in the Waitara area this year caused sewage discharges.
In the most recent incident, in March, a blown gasket caused effluent to spill near the Waiongana Stream.
The Taranaki Regional Council has told the district council to inspect the entire pipeline between Waitara and the New Plymouth wastewater treatment plant.
Regional councillor Neil Walker said there was a suspicion regular maintenance was not being done in order to cut costs.
"It's always easy in a period when cost control is paramount to put things off and it's important that people do remember that this is a fundamental and important issue and they need to address it."
The other discharges this year involved a pumping station failing, an alarm system not being triggered and a circuit breaker cutting power supply.