Costs associated with the contamination of Havelock North's water supply last year have soared to nearly $3.5 million.
The contamination in August led to more than 5000 residents becoming ill with gastroenteritis, and has been linked with three deaths.
An estimated $3,448,211 has been spent by the Hawke's Bay District Health Board, and Hastings District and Hawke's Bay regional councils.
Hastings Mayor Lawrence Yule described it as a "massive amount of money".
So too regional council chair Rex Graham, who said the total cost "probably didn't need to be that large if we co-operated right from the beginning".
While the bulk of the total has been spent by the regional council - with costs of $1,484,800 for the inquiry and its own investigation - the district council has come under fire for spending close to $1million in legal and investigation fees.
Taxpayers' Union Executive Director Jordan Williams said council was putting ratepayers in hot water, with this amount "beginning to look like the tip of the iceberg".
"While it is absolutely essential for the causes of the water contamination to be identified, we are concerned that the Hastings District Council is spending so much on lawyers and communication strategies, when this should really be about science and getting to the bottom [of] the matter," he said.
Mr Yule said the "vast bulk of the money spent, more than $700,000, has gone on exactly the kinds of work the Taxpayers' Union is recommending" including technical and scientific investigation.
Mr Graham said a lesson in co-operation needed to be learnt - as well as the Government inquiry, the regional and district council's spent over $500,000 on its own prosecution.
The regional council spent $444,251 on its own investigation, which saw charges laid against the district council - their costs associated with the prosecution totalled $71,000 in legal costs.
The prosecution ended after regional council dropped its two charges.
The cost of the outbreak for the Hawke's Bay District Health Board had also increased.
It was about $766,000 at the end of 2016, however, yesterday a HBDHB spokeswoman said the costs were now estimated to be close to $1million.
Meanwhile the release of the first of two reports from the Havelock North drinking water inquiry panel's investigation has been delayed until May this year.
Originally set down to be delivered to Attorney-General Christopher Finlayson this Friday, the inquiry sought Cabinet approval to extend the timeframe.
Announcing the time extension request, Mr Finlayson said it was due to a number of reasons including delays caused by legal action between the Hawke's Bay Regional Council and the Hastings District Council, delays caused by the need to ensure the interim safety of Havelock North's drinking water; the inquiry's decision to adopt a two-stage approach to the inquiry, and the underlying complexity of the statutory and regulatory regimes involved.
Hastings mayor Lawrence Yule said the delay was regrettable given the council and community wanted the results of the inquiry as soon as possible.
"I understand and respect the reasons for the delay - this is a big deal and has to be done properly," he said.