The official number of suicides does not give the true picture of how many people are killing themselves, says the former chief coroner.
The latest figures show 564 people committed suicide in the year to July last year - the highest number since records began eight years ago.
But Judge Neil MacLean said that figure did not include deaths that resulted from mental illness, or where people were on drugs or drunk.
He said a GP's claim that the true number of self-inflicted deaths may be considerably higher could well be right, since a suicide ruling had to meet a particular legal standard, and it must be clear the person intended to take their own life.
He said the law was a blunt instrument.
"Suicide is a legal term. As such, it's useful up to a point, but if you just focus on those cases which are found by a coroner to be a suicide, you may well be missing the bigger picture of self-harming, destructive self behaviour-types of deaths that actually occur."
Suicide prevention as important as road safety - doctor
A doctor working in mental health said he would like to see as much attention paid to suicide prevention as road safety.
Peter Watson, the clinical director of mental health for Counties Manukau District Health Board, said there is still a reluctance to talk about emotional wellbeing and suicide.
He said more people die from mental illness and suicide than on the roads, and he would back a national prevention campaign similar to the Transport Agency's road safety advertising.
"What I think we do need to do is have a much broader, wider discussion and debate about suicide prevention.
"It's actually, for many people, a really frightening and scary topic."
Where to get help:
Lifeline: 0800 543 354 (available 24/7)
Suicide Crisis Helpline: 0508 828 865 (0508 TAUTOKO) (available 24/7)
Youth services: (06) 3555 906
Youthline: 0800 376 633
Kidsline: 0800 543 754 (available 24/7)
Whatsup: 0800 942 8787 (1pm to 11pm)
Depression helpline: 0800 111 757 (available 24/7)
Rainbow Youth: (09) 376 4155
If it is an emergency and you feel like you or someone else is at risk, call 111.