Crime is at its lowest level in 24 years but the percentage of offences that police solve is also dropping - less than half of all cases.
But police say their resolution rate is one of the best in the world and would rather prevent crime than work on improving the number of recorded offences solved.
The Police Association and a victim support group say police need more funding because a redistribution of resources to frontline staff has left a gap in how crimes are investigated.
Crime statistics for last year were released yesterday, revealing a 7.5 per cent drop in recorded offences on 2011. The figures are the lowest since electronic records began.
The largest decrease was in Waitemata District, where recorded crime fell by 12.4 per cent. Other significant drops occurred in Auckland City (down 12.1 per cent), Counties Manukau (down 11 per cent) and Waikato (down 7.5 per cent).
Acting Commissioner Viv Rickard said this was a good result and that police were pleased.
"We've really put in place over the last couple of years our prevention strategy and that's really focusing our people on preventing crime, rather than just responding to crime and investigating crime."
Four years ago, police set the target of decreasing recorded crime by 13 per cent by 2014-15. Mr Rickard said they were ahead of schedule in achieving that. But in those same four years, the resolution rate of crimes has also dropped.
In 2009, 47.8 per cent of recorded offences were solved and following a declining trend, last year that figure had dropped to 47 per cent.
The resolution rate is the percentage of recorded offences in a year that are resolved within 14 days of the end of that year.
Mr Rickard defended the drop in resolution rates, saying the focus is on reducing crime.
"We believe that it's better to have fewer victims of crime than it is to let people commit crimes then be good at catching them afterwards. Our most important job is to prevent crime from occurring."
Sensible Sentencing Trust spokesman Garth McVicar said it was great to see crime dropping, but it was important to have offenders caught.
"From the feedback we're getting, the victims are noticing a re-focusing of funds into the frontline staff, which we're very supportive of, but that has probably [translated into] a reduction in the solving in the crimes. There needs to be a re-juggling of the funding available."
The police budget has been frozen for two years and is likely to remain that way for another three.
On crime rates in general, Prime Minister John Key said it was the lowest in 24 years, which he put down partly to increased visibility of police on patrol. He said foot patrols had increased by 70 per cent.