Labour leader Phil Goff says his party has done more to stem violent crime than the government's new three strikes policy will ever achieve.
National and Act have agreed on the proposed law which will see third-time serious offenders get the maximum sentence and no chance of parole.
But Mr Goff says changes in 2002 led to an additional 2,500 criminals being locked up and the new changes would only imprison a further 12 offenders a year.
In 20 years 288 offenders are projected to be in prison under the policy.
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