"The current wording prevents police from retaining up to 1200 sets of identifying particulars per year for youth who have a charge proved in the youth court, and for whom have an order is made by a judge. Those orders range from discharge right through to supervision with residence.
"A person could potentially challenge a conviction that was based on evidence from improperly retained fingerprints. This process in itself could be a time-consuming and costly process. Such an appeal may also lead to victims feeling revictimised."
Police had been holding hundreds of records that should have been destroyed under the present law, and have now been destroyed, she said.
The bill amends the Policing Act 2008 to restore the legal position under the Police Act 1958.
It was announced in the urgency motion earlier this week, but its name and nature was kept secret because of fears it might lead to a flood of legal challenges.
The Labour Party was informed of the bill earlier in the week and will support it, but Green MP Keith Locke said his party was only informed last night.
"The public didn't have any chance at all of finding out anything about this bill until we started debating it in this house.
"Any people who might be concerned about the legal issues involved in this are totally shut out of this process."
Maori Party MP Rahui Katene questioned why the name of the bill had to be kept secret.
"Legislation is being introduced under urgency and under plain cover to empower the police with the ability to store fingerprints and photographs of our arguably most vulnerable citizens, our rangatahi (youth)."
Police became aware of the problem in 2010, and the bill took so long to come before the House because of discussions between police and officials to ensure it was drafted properly.
Ms Collins said if the law was not fixed, it would prevent police from stopping re-offending youths.
"Any future re-offending by the same people will be more difficult to detect. Identification of young repeat offenders is a key tool to assisting police prevent future offending and stopping offending grow in severity over time, and providing some reassurance to victims."