The gangs making up New Zealand's soaring prison population

There are more than 26 gangs in New Zealand prisons, making up 40 percent of the muster.

That's according to an Official Information Act response to Newshub from Corrections, which shows the Mongrel Mob has by far the most numbers of all the gangs.

They're followed by Black Power, the Crips, the Killer Beez and Head Hunters MC respectively.

Corrections says most prisoners join gangs out of genuine interest, or for self-preservation.

Most new 'members' inside prisons are likely to be associates of existing gang members, as the formal recruitment process hasn't yet taken place.

From June 2013 to March 2018, the prison population has increased by 23.8 percent. In that same time period, the proportion of prisoners with gang links has increased by 82 percent.

The fastest growing gang over the past five years has been Head Hunters MC, followed by the Killer Beez and Bandidos MC.

The gangs listed by Corrections are those formally recognised on the National Gang List.

The 'Other' category includes members or associates of Crips and Bloods, which are the third and sixth most prominent gangs in prisons respectively.

Inside prisons, gang-related insignia, drawing, carving, clothing and posters are banned, and gang colours aren't allowed to be worn.

Staff assess the gang status of inmates through observation, their self-reporting and third-party reports, as well as by gang-related tattoos or insignia.

The statistics collected by Corrections also include prisoners who've patched over to other gangs while behind bars.

Figures obtained by Newshub under the Official Information Act show that more prisoners than ever are gang members, and LA street-style gangs such as the Crips, the Bloods, and the Killer Beez are on the rise and attracting young men.