The Maori Party says legislation restoring the police's right to keep fingerprints and photographs of youth offenders means such people will always be considered criminals.
Legislation passed by Parliament under urgency on Thursday allows those details to be kept in all cases except when a young person is acquitted.
Maori Party police spokesperson Rahui Katene says the law should never have been passed under urgency and the public should have been consulted.
Ms Katene says because of the legislation youths won't be able to leave their mistakes behind. It tells them, she says, that they'll always be watched and that their future is for a life of crime.
The legislation passed by 106 votes to 13 with the Greens, the Maori Party and Independent MP Chris Carter voting against.
Changes made to the Policing Act in 2008 unintentionally made storage of fingerprints and photographs of young people appearing before the Youth Court illegal.
Under that law, those details could only be kept if there was a conviction and a referral to a District Court for sentence or decision.