Waikato's top cop tried to put pressure on his staff to stop the arrest of his daughter.
Area commander Superintendent Bruce Bird was the subject of an employment investigation after the incident but has been allowed to keep his job. He is also subject to an Independent Police Conduct Authority (IPCA) investigation.
Interfering with the arrest of a friend or family member is a conflict of interest and a breach of police policy.
Bird's daughter was arrested after a domestic incident in January and taken to Hamilton Central Police Station, sources told the Herald.
Soon after, Bird - who has been Waikato's top cop since 2014 - found out about the arrest and phoned the senior officer on duty and put pressure on him to stop the arrest from happening.
Despite his interference, the woman was still processed and arrested. The Herald understands the prosecution was handled outside the Waikato district and she was given diversion.
The senior officer who was on duty when Bird's daughter was brought in abruptly quit police shortly afterwards, the Herald understands.
The officer, who the Herald has chosen not to name, then filed an official complaint with the IPCA. An investigation is still ongoing.
A police spokesman confirmed Bird was the subject of an employment investigation following a complaint from a member of staff.
"This related to a telephone conversation between Mr Bird and this individual regarding a member of Mr Bird's family," he said.
"The matter was subject to an internal investigation and resolved through an employment process.
"Mr Bird accepts that he made an error of judgement in relation to the telephone conversation, and has apologised to the individual involved."
Bird remains in his current role.
Police were "not aware of anyone who has left police" over the incident, the spokesman said.
Police would not confirm the charge laid against the daughter, nor the outcome.
All staff were expected to "act in accordance with the core values of police", the spokesperson said.
"Police have a Code of Conduct and relevant policies, including a conflict of interest policy. We take any complaint about a member of staff seriously, and any steps taken are always dependent on the specific nature of each matter."
The IPCA confirmed it was nearing the completion of its draft findings, but as it was an internal investigation the findings would not be made public.
The Waikato Police Association was unaware of any complaint or issue involving Bird when contacted by the Herald.
Police sources spoken to say they were shocked by the senior staff member's sudden departure.
It's understood the senior officer at the centre of the inquiry is subject to a confidentiality agreement.
Bird declined to comment when approached by the Herald.