The Hawke's Bay Regional Council has laid charges against the Hastings District Council in connection with the contamination of Havelock North's water in August.
The regional council has charged it with resource consent breaches, which it said were discovered during an investigation of the contamination.
The outbreak in August, in which about 5000 people became sick with gastrointestinal illness, occurred when a bore contaminated the Hawke's Bay town's water supply with campylobacter.
The council said earlier today it had laid charges against an unnamed party "for alleged offences uncovered in the course of its investigation into the contamination".
The charges related to evidence of a breach of the party's resource consent, it said.
"If a breach is proved, the resource consent no longer permits the taking of water. [The regional council] has commenced a prosecution against the party, alleging the unlawful taking of water from the aquifer arising from the alleged failure to meet well head maintenance conditions."
In a statement this afternoon, the Hastings District Council confirmed it was the charged party.
It said the charges had been laid under the Resource Management Act for a technical breach of the district council's resource consent conditions for taking water from Brookvale Bores 1 and 2.
Hawke's Bay Regional Council chief executive Andrew Newman said the drinking water contamination had a devastating effect on the Havelock North community, with wider regional impacts.
The council was "very keen" to uncover the cause of the contamination and make sure it did not happen again, he said.
More than 15 people were working on the investigation, including environmental scientists.
A government inquiry into the source of the water contamination will begin on 28 November.
Hastings District mayor Lawrence Yule said he thought the regional council was blaming the authority's maintenance of bores for the contamination.
"The regional council has a view, which we disagree with, and the appropriate venue and setting to determine what has happened here is the inquiry. So that's our focus and it will remain our focus, and we don't agree with what the regional council is saying.
"It is disappointing with the government inquiry about to start that the regional council has pre-empted that process by taking this prosecution action."