The number of arrests for cocaine possession and use in NSW has increased by nearly 50 per cent, with illicit drug researchers saying the state is in the grips of "vicious circle".

The figures, released by the Bureau of Crime Statistics and Research (BOCSAR) today, show in the 12 months leading to March 2018 there were 3,114 arrests for cocaine possession and use — 980 more than the same period the previous year.

BOCSAR executive director Dr Don Weatherburn said the state was in the middle of a "vicious circle" with the decreasing cost of cocaine making the drug more accessible.

"When you see an increase in arrests like this [it] usually means there are more of those drugs getting into the community rather than police are simply becoming more effective at catching them," Dr Weatherburn said.

Speaking after releasing the report, Dr Weatherburn said police crackdowns on illicit drugs including heroin and methamphetamine had helped curb their proliferation, but it was only a matter of time before another drug replaced them.

"Whenever they get on top one drug another drug tends sooner or later to come into the play," Dr Weatherburn said.

"It'll eventually get very risky to deal or traffic cocaine, that's certainly what the police hope to achieve. That risk means they demand higher prices, and if the prices go up consumption starts to go down again."

NSW Police Commissioner Nick Fuller said authorities would continue to target organised crime networks responsible for the distribution of illicit drugs.

"Our focus is community safety and we won't tolerate behaviour that risks the wellbeing of others," he said.

Sexual and indecent assault offences also up

The new crime statistics also revealed the number of sexual and indecent assault offences have also increased by 7.2 and 6.3 per cent respectively.

Dr Weatherburn said the figures indicated assault victims were more willing to report crimes.

"I suspect a lot of that increase is due to more cases coming to light rather than an actual increase in incidents of these offences," he said.

"The royal commission has certainly encouraged people to report those offences where previously they wouldn't have."

Trends in the 15 of the other 17 major crime categories have decreased or remained stable.