Gangs have increased control of the methamphetamine market in Northland and the South Island, a new survey has found.

New Zealand Drugs Trends Survey was completed by more than 13,000 New Zealanders between August 2022 and February this year.

Research leader Chris Wilkins says the highest levels of meth being purchased from a gang member are in Northland, Canterbury, Nelson and Marlborough.

He says the high level of gang selling in the South Island may be the result of established North Island gangs reportedly expanding meth markets in the south to take advantage of higher prices.

The survey found 41 per cent of respondents in Northland reported buying from a gang member, with 39 per cent in Canterbury and 38 per cent in Tasman/ Nelson and Marborough.

Wilkins also says new gangs formed by 501 deportees in the South Island were using international connections to provide new sources of meth supply.

The survey found rising drug purchasing from social media and messaging apps.

Researcher Robin van der Sanden says these markets were taking advantage of social networking apps that featured self-deleting messages and encryption to organise transactions between buyers and sellers.

For cannabis purchasing, the NZDTS showed there were higher levels of people buying from gangs and drug houses in the East Coast and Central North Island.

"Cannabis markets are traditionally known for their low social impact, generally involving private transactions among people who know each other," Wilkins says.

"In contrast, the sale of cannabis via gang-controlled 'tinny' houses increases the risk of victimisation and inter-gang violence".

A significant minority of NZDTS respondents reported experiencing victimisation while purchasing drugs in the past six months, including receiving fake and unsafe drugs.

Finally, a small group of repondents reported purchasing drug types like MDMA and psychedelics from encrypted 'darknet' websites with cryptocurrency, like bitcoin.

Wilkins told Morning Report social media and encrypted apps were opening up access to younger people.

"Inevitably you have to go to the physical location to pick up drugs ... there's opportunities for scams and victimisation, and some people have been victim of that including physical violence."

- RNZ.