Twenty offenders are on their final warning under the three-strikes legislation introduced in 2010.
The next time they offend they will get the maximum prison penalty with no possibility of parole, under the provisions of the Sentencing and Parole Reform Act 2010.
Figures released to Radio New Zealand's Nine to Noon programme by the Ministry of Justice show most were convicted of robbery or aggravated robbery.
Victoria University criminologist John Pratt told the programme the legislation is not targeting the most serious offenders it was intended to deal with.
He says research on the deterrent effect of such legislation shows it does not work.
In a statement, Justice Minister Judith Collins says the legislation is working well and as intended, and the Government has no plans to change it.