New Zealand's leading authority on gangs says that police gang statistics have been sharply over-estimated and are inaccurate.
The figures were used on Wednesday by National Party leader Judith Collins to call for harsher action on organised crime across the country.
She said the number of gang members in Wellington have almost doubled in three years.
However University of Canterbury lecturer Jarrod Gilbert told Morning Report this is simply not true and there are problems with how the numbers are collected.
"It's incredibly easy to get on that list, because a police officer can see someone's wearing a patch, or whatever it might be and so their name goes on the list, but then if people leave the gang it's very very hard to identify when that occurs.
"The list is growing very very quickly but it doesn't shrink correspondingly."
There are gangs on the list that don't exist, he said.
"It could be as much as double the reality."
Gilbert said there is growth in the gang scene but how the growth is measured needs to be looked at.
He said the numbers are helpful for police to have a sense of who is out there, but not good to use for policy.
"We need to be working on more accurate figures."