Court action is a possibility if Central Hawke's Bay council continues to breach its resource consents for its wastewater treatment plants.
Regional council group manager resource management Iain Maxwell said the consents that were currently under review were for the Waipukurau and Waipawa plants.
"HBRC has made no determination about whether or not to prosecute at this stage."
Mr Maxwell said the resource consents allow for a certain number of "exceedances" each year.
"Currently Waipukurau has reached its limit and Waipawa is two away," he said.
"These are the latest figures."
According to the regional council, CHB council upgraded its wastewater treatment plants in 2014 to meet new standards required under new resource consents, which came into effect in October of that year.
Earlier this year abatement notices were served on the CHB District Council after it failed to meet the required discharge standards.
At last week's council meeting Mr Maxwell said there have been ongoing issues with phosphorous and E. coli levels at the plants.
"So we have sought advice to clarify when we might consider we should be assessing compliance with these conditions given that they have an annual cycle of monitoring."
Mr Maxwell said they would soon have the most recent test results from the plants, with test samples taken every two weeks.
"We will at that point consider whether certainly Waipukurau is non-compliant and how close Waipawa is to non-complying if it has had further exceedances," he said.
"What we will do at that point is look at those results and then take some advice as to what our next options are which may include a formal prosecution."
Yesterday, Mr Maxwell said the regional council had not yet made a determination about whether or not to prosecute at this stage.
"This will depend on the results of our investigation into this matter," he said.
However, he said from his council's perspective meeting the required discharge standards was not negotiable.
CHB council chief executive John Freeman said while the regional council had a right to take his district council to court, it would be counter productive as both councils would be using ratepayers' money that could instead be used to improve the network.
"I don't have a problem with that. We have consents and we should be sticking to them, we are doing everything we can," he said.
"[But] taking people to court while it is right or within the rules they can do it but it is really counter productive."
Mr Freeman said his council had only been in breach of the consents since new rules were introduced in 2008.
"So they [the regional council] are looking into those consent conditions to make them more realistic," he said.
"But again at the end of the day we are not shirking our responsibilities but stuff takes time.
"At the end of the day this is a 10-year process and we will make big strides in the first year or two and then things will take a little longer.
"It's a work in progress."
Both Mr Maxwell and Mr Freeman said the councils were working together to ensure the required discharge standards from their plants are met.