New Zealand's leading expert on gangs says that gang statistics from New Zealand Police aren't suitable for use by politicians.
The figures were used on Wednesday by the National Party leader Judith Collins to call for harsher action on organised crime across the country.
University of Canterbury lecturer Jarrod Gilbert told Morning Report the statistics work well for intelligence purposes, but not so much for policy.
Dr Gilbert said it's easy for a person to get put on the gang list, but much harder to get off it.
"The list is growing very, very quickly, but it doesn't shrink correspondingly. So we can't rely on this data to say how big this scene is, or the degree to which the growth is occurring."