A report into how police handled media queries about the so-called Roastbusters case says there was a systemic breakdown in communication, Radio New Zealand reports.
Police are still investigating a group of young men who boasted online about having sex with drunk teenage girls.
The Independent Police Conduct Authority is reviewing the police handling of the criminal investigation but can't release its report until the police case is closed.
However, the authority has also investigated complaints from Police Minister Anne Tolley and Labour MP Jacinda Ardern about the way police handled media queries.
Police originally told reporters they hadn't been able to investigate the group because no one had made a formal complaint. However it emerged that four girls had come forward, and one had made a formal complaint.
Authority chair Judge Sir David Carruthers said police did not deliberately mislead the media and no individual officer can be criticised, but the mistakes undermined public trust and confidence in the police.
Police said they accept the authority's view and regret they did not get their media communications right.
