New figures from police wastewater drug testing reveal a spike in Aucklanders' MDMA use and a steady increase in cocaine use in the city.
Despite population differences, the results show drug use is largely more prevalent in Christchurch than it is in Auckland.
Wastewater testing began in Christchurch and Auckland in December last year, and a new testing operation in Whangarei started three months ago.
Data is collected from the wastewater facilities for one week every month and analysed for traces of methamphetamine, MDMA, or ecstasy, cocaine heroin and a-PVP.
The first three drugs were picked up in wastewater in all three of the testing spots. However, authorities overseeing the new pilot programme have so far failed to detect heroin and designer drug alpha-PVP.