An audit of the staging of the V8 Supercar races in Hamilton has found the city council did not carry out a business case before committing to the project.
The Audit New Zealand report was commissioned by the new council following last year's local-body elections, after concern was raised over the true cost of the event.
The report says the overall cost to the city has been about $36 million. Yet the idea of holding the race in Hamilton was sold to ratepayers on the basis it would cost the city just over $7 million.
Audit New Zealand says no due diligence was carried out on the promoter organisation, which was experiencing financial difficulties before the contract was even signed.
The report also found that reporting by council management to elected councillors was not satisfactory, particularly on the total cost.
It says both management and council showed a lack of caution in committing the city to the event.
Earlier this month, the council voted to end its contract with V8 Supercars after next year's race in April.