A non-sworn police employee forcibly pinned a female colleague to a table and simulated a sex act on her, the independent police watchdog has found.
A number of colleagues witnessed this behaviour but did not report it as they thought he was "joking".
The Auckland custody officer is a non-sworn police employee who works in the courts, managing detainees.
The Independent Police Conduct Authority (IPCA) found the man's actions were criminal, and he was charged, pleaded guilty and resigned.
The investigation found he similarly sexually harassed two other employees, and sent videos of prisoners to colleagues on Snapchat.
The actions were in 2018 but the report was delayed until the court matters finished.
Relieving Auckland City district commander superintendent Shanan Gray said police accepted the findings.
Gray said police stood the officer down and notified IPCA after learning about his behaviour.
The officer was convicted on two charges of male assaults female.
"We're incredibly disappointed by the behaviour of this individual and as soon as senior Police leaders were made aware of the behaviour it was investigated and addressed," Gray said.
"Our people who were subjected to this behaviour have been well supported throughout the investigation and we have been working on a number of initiatives, aimed at improving the culture within our custody unit. This work remains ongoing."