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The Government plans to introduce a comprehensive management scheme similar to one run in Britain, in which officials keep track of the addresses, jobs, family relationships and other details of serious offenders once they are released from prison.
It would cover dangerous repeat violent offenders and sex offenders. The information would be available to government agencies and not the public.
Police and Corrections have begun policy work, including producing a report and a timeline for introducing the management scheme, including the register of sex offenders.
"It's quite a big piece of work. It's not just a list of offenders; it's a management system that manages offenders from the time they leave prison, almost for the rest of their lives."
Mrs Tolley said she couldn't rule out human error, but the Government would take security seriously given the privacy breaches with ACC, Work and Income, the Inland Revenue Department and the Ministry of Education's Novopay payroll system.
"It's paramount, because yes it can be very detrimental to someone who is being well managed in the community if suddenly a community finds out their history. You do have to make sure you have a secure system."
Tolley has rejected criticism from Labour that a register of sex offenders would only contain information already held by the Ministry of Justice.
In 2004, a Parliamentary select committee dismissed a member's bill to set up a sex offenders register, because police and experts in the area had advised it would not be helpful.
However, Mrs Tolley said offenders were not being adequately monitored once released from prison.
"We literally wait for them to reoffend before we pick them up again."
Labour's police spokesman Kris Faafoi said frontline officers would struggle to monitor those on a register.
"I am sure frontline officers will be left asking 'who is going to do that?' at a time when National is cutting back our frontline policing capability," said Mr Faafoi.