Serious assaults, largely fuelled by booze, are on the rise, especially amongst young men, Polynesians and those in poor neighbourhoods, according to Otago University research.
The research "throws into doubt" police and Ministry of Justice claims New Zealand is becoming a less violent place, the authors say.
"The trends we have observed are concerning, especially since there is no evidence of any recent abatement," lead author Professor John Langley says in the study, published in the New Zealand Medical Journal on Friday.
Excessive alcohol consumption was a common factor behind many assaults, which showed the need for the Government to effectively tackle the alcohol issue if it wanted to significantly reduce serious assaults, he said.
There was sufficient evidence to show that reduced alcohol advertising and higher taxes on alcohol were likely to have a significant and relatively rapid effect on assaults, he said.
When annual crime statistics were released earlier this month, police bosses said New Zealand was becoming a safer place to live.
Acts intended to cause injury, which are mainly assault-related offences, dropped by 6.8 percent on the previous year and police figures show serious assaults resulting in injury dropped in the last four years and are back to levels of the mid 1990s.
But Prof Langley said for males, particularly in the 15-to-24 age group, the numbers of serious assaults - where the victim had a six percent or worse chance of dying - had risen dramatically between 2004 and 2009.
In New Zealand between 2000 and 2009 there were 8006 serious non-fatal assaults. More than three-quarters of the victims were male.
Maori accounted for almost half of female serious non-fatal assaults, and nearly one-third of males in the same category.
Pacific Islanders also featured prominently among the male victim statistics, having a rate only slightly lower than Maori males.
The study also showed that if you live in a deprived household or neighbourhood, your risk of serious assault is much higher.
NZN