Methamphetamine use has surged among people who have been arrested, according to a new study.
In Christchurch, use of the drug increased from one in five of those arrested in 2012, to one in three last year.
Massey University's annual arrestee drug use monitoring report tracks substance use among people arrested by police.
Last year, 835 detainees were interviewed at four police stations across the country.
While alcohol and cannabis use is falling, methamphetamine use is on the rise.
In 2015, 36 percent of people detained by police reported using the drug, compared with 28 percent in 2012.
The study's author, Chris Wilkins, said several factors made the drug popular and accessible.
"There's been an increase in methamphetamine supply in this part of the world.
"New Zealand has been reporting record seizures of methamphetamine at the border."
This was consistent with places like Australia, he said.
Dr Wilkins said domestic factors, such as the Canterbury post-earthquake rebuild, had attracted construction workers.
"They tend to be young, earning quite good money, so a possible explanation is that they are creating extra demand for methamphetamine and other drugs."
Drug Foundation executive director Ross Bell was not surprised by the data.
"A group of New Zealanders have been using methamphetamine and using quite heavily and quite problematically.
"Those people who have an addiction, who are beginning to turn to crime, are now showing up in some of this police research."
Mr Bell said health interventions could break the addiction and crime cycle.
Deputy Police Commissioner Michael Clement said the government would spend almost $15 million on anti-drug initiatives this financial year.
He said $6.2m of that would go towards disrupting the flow of drugs from southern China to New Zealand.