The Justice Minister is standing by legislation that would allow very high-risk offenders to be detained pre-emptively after they have served their prison sentence.
A High Court judge would be able to issue a public protection order for offenders the Crown can show pose a very high risk of committing serious sexual or violent crimes.
The law change was announced by the National Party during the 2011 election campaign.
At the time, Justice Minister Judith Collins used serial rapist Stuart Murray Wilson as an example, as he was convicted before preventive detention was available.
The Labour Party is supporting the bill for now, so it can be examined further by a select committee.
However, it says the case for the change will have to be proven because as it stands, the legislation is a breach of human rights.
The legislation passed its first reading 106-14 with the Greens and Mana opposing it.
It will now be considered by Parliament's Justice and Electoral committee.