The Auditor-General is investigating Auckland councillor Cathy Casey's complaint that a secret report on the V8 supercars was hidden from the council by its standalone events body.
Councillors approved $10.6 million on Thursday to ensure the return of the supercars to Pukekohe after Auckland Tourism, Events and Economic Development (Ateed) refused to show them a report on the financial position of parties involved in the event.
Councillors and the public have also been unable to see a "detailed risk review" referred to by Ateed because Auckland Council chief executive Doug McKay said it did not exist as a single document, but as a "multi-faceted" review of the risks.
"I am dumbfounded that a council-controlled organisation can refuse to disclose to councillors a ratepayer-funded due diligence report ahead of a major decision involving $10.6 million of ratepayers' money," Dr Casey said in a letter to Auditor-General Lyn Provost.
"This rushed decision ... was made in the absence of crucial risk and due diligence information."