Auditor-General Lyn Provost has singled out ACC's board and management over the handling of the Bronwyn Pullar affair.
While raising the alleged failure of ACC board and management to recognise the risks of Ms Pullar's "wider allegations of illegality and fraud", Ms Provost had no view on the allegations and did not investiate them.
Her report investigated specifically the interactions between Ms Pullar and ACC chairman John Judge and deputy chairman John McCliskie.
Ms Provost says her inquiry found no evidence Ms Pullar gained an advantage by approaching Mr McCliskie for help with her case – a direct approach to a board member rarely made by any claimant.
"However, the board had no formal policy to guide board members on communication with individual claimants.
"Of greater concern was ACC's failure to recognise Ms Pullar's wider allegations of illegality and fraud as risks to the organisation.
"ACC management and the board members concerned failed to appreciate the risk that those allegations presented."
They were "so focused on the appropriate separation of governance and operational matters that they did not recognise these issues as possible symptoms of systematic failure."
The Auditor-General's report is one of two reports released today into the affair.
The other, from the privacy commissioner, criticises ACC for having an "almost cavalier attitude" to the privacy of clients.