Dangerous repeat violent offenders and sex offenders could be monitored for the rest of their lives after release from prison, says Police and Corrections Minister Anne Tolley.
She wants to develop a comprehensive management scheme similar to one run in Britain and says a law allowing it could be passed by the 2014 election.
The Government also has a measure before Parliament that would allow ex-prisoners to be sent back to jail indefinitely if the High Court deemed them dangerous enough.
At present, the maximum time a former prisoner can be supervised after release is 10 years, as in the case of Stewart Murray Wilson, who is living in the grounds of Wanganui Prison.
Mrs Tolley returned last week from visiting the Multi-Agency Public Protection Arrangements group (Mappa) in London.
It monitors about 58,000 registered offenders who are deemed to pose a serious risk of harm to the public on their release.
"They do a risk analysis of them and keep track of them essentially for the rest of their lives," she said.
At a minimum, the offenders were required to register once a year.
Officials kept track of their address, job, family relationships and other things depending on the individual.
The officials kept an eye on their propensity for offending again but also worked with them to help them find another job if they lost one, or find housing.
Mrs Tolley said she was worried that once repeat offenders finished their parole or supervision orders they went out into the community.
"Take someone like Stewart Wilson - he's on parole and then he is on an extended supervision order for 10 years, which is a really close monitoring of him, but at the end of that period he is finished and we just walk away."
She hoped that because Wilson was older, his opportunities for reoffending would be few, "but there are some younger ones who will just disappear out into the community".
Asked about civil liberties concerns, she said most offenders found it helpful to have that sort of structure in their lives "and know if something goes wrong, there is someone keeping track of them and they are not on their own out in the community".
Mrs Tolley said the Police and Corrections had started doing policy work on the scheme before her trip but it became clear to her in London that it had to be a joint programme.
She has asked Police Commissioner Peter Marshall and Corrections chief executive Ray Smith to make it a priority so she could take a paper to the Cabinet by the middle of next year.