Gaps, delays and inconsistencies in the way information on suicide is collected and shared could be hampering efforts to prevent it, the Auditor-General has found.
Meanwhile, separately, a bill to change the Coroners Act - including to allow media to report a death as "suspected suicide" - has passed its final reading in Parliament.
In 2013, the latest year for which statistics are available, there were 508 suicides - or one every 17 hours.
In a report to Parliament today, Controller and Auditor-General Lyn Provost said a blow-out in wait times for coronial inquests to more than two years could be hampering suicide prevention work.
The average time for coroners to complete suicide inquiries increased between 2010/11 and 2014/15, from an average of:
- 318 days to 509 days for inquiries without an inquest; and
- 676 days to 778 days for inquiries with an inquest.
Under a system introduced last January, duty coroners pass on information about suspected suicides to district health boards immediately to allow support to be provided for local communities.
However, Ms Provost said there was no evidence that DHBs were responding appropriately to the information they received, and some local agencies were too slow to act.
Mike Scott said the Justice Ministry was aiming to complete all coronial inquiries within 300 days, so families could get decisions sooner and statistics could be published sooner.
"Timely information is really important, and the sooner information can be made available the better all round, really," he said.
"The sooner families understand what's happened - and the sooner it can be used and analysed to understand, in a broad sense, what are some of the difficult causes of suicide and what can be done to help prevent it."
The issue of which deaths were reviewed - and whether that should change - was also considered in the report.
Currently, two mortality review committees considered about 30 percent of suicides - mostly those of children, young people and mothers - which meant the rest of the deaths, mainly of older adults, went unreviewed.
"We think if more suicides were reviewed it would provide a fuller picture, and a more insightful picture of some of the complex causes and help identify ways in which it could be prevented," Mr Scott said.
Mr Scott said it was too early to tell whether the planned improvements would be effective, but the next two years were important and agencies needed to carry out their plans and report back.
Suicide reporting rules set to change
Meanwhile, media will soon be able to report a death as "suspected suicide" after a bill to change the Coroners Act passed its final reading in Parliament.
Labour was the only party to oppose the bill, saying it was concerned about removing the requirement to always undertake an inquest into a death while in official custody or care.
It was also opposed to the move to stop coroners conducting inquiries into deaths in the Defence Force.
Chief Coroner Judge Deborah Marshall said last month official figures for suicides in New Zealand did not give the full picture, as ruling that a death was a suicide had to pass a legal threshold.
Where to get help:
If it is an emergency, and you feel like you or someone else is at risk, call 111.