Gangs committing most of the crime in NZ?

This RNZ reported statement from Corrections Minister Anne Tolley, on the back of the Springhill riots, intrigues me:

She said most crime in New Zealand is committed by gang members.

How does she know?

One would assume that the number of gang members in prison might provide a pointer but I don't believe that has been measured since the Prison Census was discontinued in 2003, at which time patched and associates made up 11.1 percent of the prison population.

Now if the percentage was unchanged (unlikely) and her statement was true, that reflects very badly on those charged with detecting crime and locking up offenders.

There were 376,013 crimes recorded in NZ in 2012.

Yet according to National MP Todd McClay:

 Police estimate there are 3,500 patched gang members in New Zealand.

(Revealing comment at the bottom of that op-ed)

The Sensible Sentencing Trust claims there are 21,882 gang members and affiliates. That's very specific.

Anyway, the numbers don't  stack up.

I've tried to verify that Tolley actually said this, but there's no press release on the matter.

Don't you wish that journalists would be a bit sharper and dig deeper when confronted with quite startling claims?

Jarrod Gilbert, who has researched gangs for a decade says,

"There's a lot of hysteria which is unnecessary for the most part."

So what's the truth of it? Even if she intended 'violent' crime I'm dubious about the accuracy. (And when gangs are committing crime it's often against each other or other gangs though that's not really relevant to the topic of this post.)

Finally, after a bit more searching I've found this from a 2009 paper prepared for Parliament about young people and gangs:

Recorded apprehensions where the offender was recorded as gang affiliated at the time of offence declined from 4,711 in the 2002/03 fiscal year to 3,706 in 2004/05 but then increased to 6,392 in 2005/06. [19]   The Department of Corrections’ Census of Prison Inmates and Home Detainees 2003 found that 62 percent of sentenced gang members were imprisoned for violence or sexual violence. This was slightly higher than for those without gang connections (58 percent). [20]  
As at 16 May 2007 a total of 1,471 prisoners were identified as actively affiliated with gangs. The largest numbers were affiliated with the Mongrel Mob (523) and were Black Power (426). [21]   This compares to a total prison population at 30 June 2007 of 8,083. [22]   In June 2008 the Minister of Police Hon Annette King said Police estimated the total number of patched gang members and associates was between 3,000 and 3,500. [23]   Police Association President Greg O’Connor thought the figure was higher – probably over 3,500. [24]  

I can't find any basis for the Minister's claim. It could come from Victimisation Surveys which capture non-prosecuted crime but....I'm still skeptical. Looks like she was wrong or mis-reported.