A Northland residents' group is planning to bill the Auditor-General's office for $54 million over an ongoing dispute.
The Mangawhai Ratepayers and Residents Association lost legal action it took against Kaipara District Council over the cost of a new major wastewater treatment project.
Chairman Bruce Rogan said the bulk of the invoice was made up of the cost of the project, minus the price the community was originally consulted on.
"That was $17m and when the final invoice came in from the builders, it was $63m," he said.
"So I took the difference between the two and said 'well, that loss is at the door of the Auditor-General', because the Auditor-General was the party responsible for looking after the interests of the community in that time."
Further court action possible
The Mangawhai Ratepayers and Residents Association applied to the High Court in 2013 for a judicial review of the legality of the rates levied to fund loans the council had failed to consult ratepayers about.
The court found the borrowing was unlawful but could not find the rates were also illegal as Parliament had passed a special bill to validate them.
Earlier this month, the Court of Appeal dismissed the association's appeal against that ruling and ordered it to pay the council's costs.
Mr Rogan said the association was still considering a further appeal to the Supreme Court.