Auditor-General Lyn Provost says she is considering requests for an independent inquiry into ACC.
National MP Nick Smith resigned from Cabinet on Wednesday after admitting that, while ACC Minister last year, he wrote a reference under ministerial letterhead for his friend Bronwyn Pullar and failed to declare a conflict of interest.
Opposition parties say an independent inquiry is needed to find out more about ACC's handling of Ms Pullar's claim, and whether there was ministerial interference.
Ms Provost says that type of inquiry would involve a significant commitment of time and public funds, and she needs to make sure she understands the issues, as well as the work being done by other agencies, before making a decision.
Prime Minister John Key has rejected opposition calls for such an inquiry, though Dr Smith himself supports an investigation.
ACC chairman John Judge has said the corporation's board will co-operate fully with any inquiry.