ACT says its policy to keep repeat, violent criminals in prison for 25 years, will not affect petty criminals.
The Government has agreed to support ACT's policy of 'three strikes' to the select committee stage, as part of a confidence and supply agreement.
The policy would mean those convicted of a third violent offence, would be sentenced to 25 years in prison, without parole.
However, a law professor in California says a similar law there has not reduced crime.
Michael Vitiello of the McGeorge School of Law says state prisons are bursting at the seams, and the situation is made worse because a third strike can be any offence, such as shoplifting.
But ACT says its bill would affect only people who commit three violent crimes.