Police Commissioner Howard Broad has announced a criminal investigation into allegations about a former senior officer.
He told a news conference on Thursday that information had been passed to him in the past couple of days about a relationship between Jon Moss, the former manager of professional standards at police headquarters, and an unnamed official of another agency linked to the police.
Mr Moss resigned last year after allegations of improperly influencing another officer. A criminal investigation at the time found no case to answer but Mr Broad says he is now opening an investigation into allegations about the relationship.
"The propriety of that relationship has caused disquiet," he says.
My decision to go, says Broad
Mr Broad also faced questions at the news conference about the announcement that he will leave his job next year.
He said that it was his decision to go, and that he had indicated to the Police Minister months ago that he would not want another five-year term when his contract expires in April. The job had taken a toll on his health and family, he said, and five years was enough.
The minister, Judith Collins, says Mr Broad is leaving of his own volition and not because of any dissatisfaction on her part.
Radio New Zealand's police reporter says police commissioners' terms are rarely extended.
Controversy 'goes with the job'
Mr Broad was in charge when the Bazley report found unacceptable sexual conduct by some police officers and systemic flaws that allowed it to happen.
The same year, 2007, police launched their controversial armed raids on suspected terrorist activity, most notably in the Urewera.
"Any Commissioner of Police is going to find themselves having to deal with controversial and difficult issues," Ms Collins says.
"It simply goes with the job. And I think the commissioner has done his very best to modernise the New Zealand Police and work very much towards the cultural changes that New Zealanders expect."
The minister says she wants the net cast wide in the search for Mr Broad's replacement, which will be undertaken by the State Services Commission.
Indicated some months ago - PM
Prime Minister John Key says he understands Mr Broad met with Ms Collins some months ago and indicated that he would be prepared to stay on in the role, but not for five more years.
The Prime Minister thanked Mr Broad, saying he'd done a tremendous job in his decades of loyal work for the New Zealand public.
Police Association Greg O'Connor says that the news is no surprise but that it would have been good for the country if Mr Broad had remained in the job.