A man is arrested in Riccarton Rd, Christchurch, after cannabis was found in his bag. (File photo)

The idea that legalising cannabis will free up police time has been described as "naive" by the boss of the Police Association, who says police spend little time dealing with cannabis-only offending.

Chris Cahill, president of the association which supports police staff and their families, said the reality is that the only targeted cannabis policing is around the dealing of cannabis.

"[Police] don't target the users of cannabis."

Marijuana dealing, which usually fell under the banner of organised crime, was "not the highest priority for police", although eradicating dealing operations helped to reduce associated crime like thefts and burglaries, Cahill said.

From July 1, an additional 11 police staff will be dedicated to fighting organised crime as part of the Government's four-year, $388 million Safer Communities Package.

"A lot of these cannabis houses are also dealing methamphetamine, so that's the main target, but at times the cannabis is included across that," Cahill said.

MAARTEN HOLL/STUFF Police Association president Chris Cahill says police devote little time to cannabis-related offending.

"But as far as people being charged with just 'possession of cannabis' offences, the vast majority of those charges are add-ons to more serious offending."

A large part of the organised crime effort was about getting money out of the hands of gangs, although there was clear evidence that shutting down a cannabis dealing house resulted in a drop in other offending. It was for that reason that most dealers, or suspected dealers, were reported, he said.

"The public tend to be pretty good at it, because they know the trouble it brings.

GRANT MATTHEW/FAIRFAX NZ The Police Association says cannabis-related crime is not the highest priority for police.

"But I'd say there's a level of frustration as to how much action they get from the police out of it at times."

Cahill did not think the level of cannabis-related crime was out of hand, though acknowledged more could be done.

"It's not the highest priority for the police, and I don't think we'd say they put too much resource into it.

"Organised crime, which this tends to fall under, hasn't necessarily had the resources put into it by police that it deserves, and that's led to a lot of frustration both by members of the public and some areas of police staff."

The discussion on legalisation of cannabis was not a simple one, he said.

"While we're probably relatively comfortable that people shouldn't necessarily be receiving a lot of convictions for just possession of cannabis, the idea of legalising it has lots of other implications.

"For instance, while an adult who smokes a joint of cannabis on a Saturday night may not be at any serious health risk, 13 or 14-year-old youths that smoke cannabis is a totally different situation, and that needs to be understood."

Police assistant commissioner of investigations Richard Chambers said police worked "extremely hard" to disrupt drug supply, reduce demand and prevent harm caused by organised crime.

"Illicit drugs cause significant harm, not only for the person using them, but for their family, friends and wider community."

Earlier this year, police conducted Operation Sam, which recovered more than 90,000 cannabis plants, as well as almost 900 grams of methamphetamine, $200,000 in stolen goods, and 130 firearms. The operation prevented an estimated $729m of associated harm.

A total of 80 constabulary staff will be recruited and dedicated to organised crime over next four years under the Safer Communities Package.