The Green Party says ACC's claim it was threatened by a claimant lacks credibility.
Police have investigated and dismissed a claim by ACC that Bronwyn Pullar threatened to keep information mistakenly sent to her.
ACC also claims Ms Pullar said she would go to the media about the breach, unless she was guaranteed a benefit for two years.
Ms Pullar has consistently denied making a threat.
The Green's ACC spokesperson Kevin Hague says the whole point of the police complaint was to distract the media from the intense scrutiny ACC was under at the time.
He says if the corporation had been the victim of an extortion attempt, why did it not complain after the meeting last December, instead of waiting three months.
ACC board chair John Judge is standing by ACC's managers and their decision to go to the police.
Investigations are still underway by the Auditor-General and the Privacy Commissioner into privacy breaches by ACC.