While neither of the two Hawke's Bay councils involved in the Havelock North water contamination were directly to blame for it, their "dysfunctional" relationship could have prevented more than 5000 people falling ill.
This was explained yesterday as part of inquiry's findings into the cause of the August contamination.
Both the Hastings District and Hawke's Bay Regional Councils were found to have failings by the inquiry - a critical one being that they had not worked "effectively or constructively together" before, or after the outbreak.
Yesterday inquiry chairman Lyn Stevens QC said while the "dysfunctional" relationship between the two prior to the outbreak might not have directly contributed to the outbreak, "at the very least it resulted in a number of missed opportunities".
"The uptake of such opportunities might well have prevented the outbreak," he said.
While Hastings Mayor Lawrence Yule said he thought the criticism about their relationship was fair, he disagreed with the inquiry's view the outbreak could have been prevented.
He did think that if they had both looked at the risks posed by the Brookvale Bores - an untreated supply in the midst of farmland - that "we might have formed a view that actually, this was riskier than we would have thought for the last 35 years".
Regional council chairman Rex Graham said he did not think they had handled the situation with the district council as well as they could have - but disputed their relationship was "dysfunctional".
He said the regional council's statutory responsibility to protect the environment meant "from time to time we run into conflict with councils".
"We need to get across there that we can do things a whole lot better," he said. "I think having the relationship at a political level such as Lawrence and I do ...being able to have a cup of coffee together or cup of tea together we can iron some of these issues out.
"We failed to do that and I think going forward we need to understand each other's issues a lot better than we have."
Mr Yule did not take personal responsibility for the poor relationship as he thought it had been between the councils' staff, rather than at a political level.
"It wasn't something that was ever brought to me as an elected person, that [there] was a problem with a relationship at that [staff] level. We just assumed that everything was being done in accordance with best practice, that was the assumption and it was probably an incorrect assumption."
The inquiry also pointed out the relationship between the two councils had deteriorated further after the regional council filed two charges against the district council - which also caused the inquiry to be delayed for a number of months.
"In the inquiry's view such a proceeding was ill advised and ought never to have been launched," Mr Stevens said, adding the prosecution seemed "bound to fail".
In response to this, Mr Graham said they had a duty to prosecute if there was a breach of the Resource Management Act.
"Generally [we] have a chat to the offending council before we do that, on this occasion we didn't do that and I think that's where we let ourselves down."
He disputed the prosecution was bound to fail, but "suffice to say at the time I thought we could have done better and now I think we could have done better" .
During the inquiry Mr Stevens added the money spent by the regional council on the prosecution - which totalled over $400,000 - could have been "more wisely used" investigating the status of the aquifers under the Heretaunga plains.