The Corrections Department has found only two out of 7000 prison volunteers are active gang members.
The department has released a review that began after a man was stood down from volunteering in Whanganui Prison because he was a patched Black Power member.
Ngapari Nui had been helping out at the prison for five years without a reported problem.
At the time, Corrections Minister Judith Collins said his volunteering was inappropriate.
The review looked at nearly 7000 volunteers, with 76 found to have some form of current or historical gang association.
It found that, of the two with active memberships, one had failed to disclose the extent of his involvement and the other was a gang associate with a conviction for producing methamphetamine.
Corrections has revoked their approval to visit prison.