The National Party says it will abolish parole for some violent repeat offenders under its proposed "life means life" policy.
Party leader John Key says this will require $314 million for a new prison and a $43 million a year in running costs.
He says the plans would see offenders serving their sentences in full if they have already been convicted of a violent crime and sentenced to five years or more in prison.
However, he says the policy still gives a second chance to offenders, who will get one chance at parole.
Speaking to reporters in Tauranga, Mr Key said 144 people have been convicted of murder since 2002.
"Ten of those would fall within the category of this being the second time in prison for a repeat violent offence, and under that basis those ten individuals, like Graeme Burton, like William Dwayne Bell, they won't get out of prison under a National Government."
Policy ineffective - Goff
Labour's Corrections spokesperson Phil Goff agrees there are a small number of offenders who should never be released, but he says current laws are enough to ensure that.
He says National's policy is designed to appeal to the public, but it will be expensive and ineffective.
Mr Goff told a media conference that tougher laws and more police must be balanced with measures to prevent crime.
"We've certainly been tough, what I'd like to see now is the building on of the policies that we've already put in place in terms of preventing crime, of stopping people becoming offenders in the first instance.
New Zealand First Party law and order spokesman Ron Mark says National's plans to abolish parole for only violent offenders shows it lacks the spine to get tough on crime.
Mr Mark says his party wants to see parole abolished altogether, as well as an end to concurrent sentences that allow criminals to serve their prison terms combined into one block.
He says he lacks confidence that National would implement this policy, let alone one that would result in fewer criminals being eligible for parole.
Good move for victims, says Trust
Sensible Sentencing Trust spokesman Garth McVicar says National's plan will take away a huge amount of anxiety for victims of crime.
He says he has seen the parole system cause a great deal of stress for victims, and the policy is a step in the right direction.
Mr McVicar believes abolishing parole for some violent repeat offenders would also deter people from committing violent crime.
However Howard League for Penal Reform president Peter Williams QC describes the plan as a backwards move.
Mr Williams says if inmates have no prospect of parole, there is no incentive for them to reform.
He says there is no evidence to suggest longer sentences reduce crime, and the argument that the policy will stop people committing crime was the same one used by those in favour of hanging.
