Justice Minister Amy Adams says new crime measures aren't a shifting of the goalposts as officials seek answers on why two key Government targets could be missed.
There has been significant success in cutting the total crime and youth crime rates, but bringing down rates of violent crime and reoffending are proving much more difficult.
Cutting violent crime by 20 per cent between June 2011 and June 2017 was one of the National-led Government's key "better public service" targets.
But with just over 15 months remaining until deadline, half the task remains. The latest information shows the violent crime rate has increased slightly since a low point in March 2014, and is now down by 10 per cent since 2011.
Progress has largely been slowed by a stubborn family violence rate, which has dropped only 3 per cent since 2011.
Ms Adams said the target on violent crime combined family violence and other types of violence.
That "conflates two different problems" - domestic or family violence, and violence in a public place.
Because of this, two "supporting measures" will now be tracked - violent offences in a private dwelling (family violence), and violent offences in public places.
Ms Adams said violence in public places was down 19 per cent since June 2011, but family violence was down only 3 per cent.
"While it's not clear why family violence is reducing more slowly ... the likely cause is increased public awareness and reporting."
Another new "supporting measure" is to track the number of criminals who reoffend within 12 months of being released from prison or starting a community sentence.
The reoffending rate (a better public service target) is down 7.7 per cent since 2011, a considerable way off the BPS goal of 25 per cent by June next year.
Progress looks more impressive if the number of people reoffending is looked at - a 25 per cent drop since 2011 - not the reoffending rate.
Labour's justice spokeswoman Jacinda Ardern said the Government had once been very confident about reaching its BPS justice targets, and the "supporting measures" appeared to be an effort to explain why that might not now happen.
Caution needed to be taken when setting targets and using data to make claims about progress, Ms Ardern said. For example, low resolution rates for some crimes meant people could be less likely to report them.
"I have seen, for instance, incidents in places like K Rd, where there is a hesitation for people to call anything in, because nothing has happened the last time they did."
Targets in reach
Reduce the total crime rate by 20 per cent by June 2018 (down 17 per cent since June 2011)
Reduce the youth crime rate by 25 per cent by June 2017 (down 39 per cent)
Targets hard to hit
Reduce the violent crime rate by 20 per cent by June 2017 (down 10 per cent since June 2011)
Reduce reoffending by 25 per cent by June 2017 (down 7.7 per cent)