The ACT Party has lined up 77 mock coffin lids against the wall of Mount Eden prison in Auckland, saying they represent people who would not have been killed if its law and order policy had been in place.
The party used the prison for its launch despite objections from Corrections Department staff.
Under the "Three Strikes and You're Out" policy anyone with a third conviction for serious violence would be jailed for life.
ACT leader Rodney Hide says all 77 victims represented by the mock coffin lids had been killed by people who had more than three previous serious offences.
He says the party's policy would eventually double the country's prison population.
Mr Hide says ACT would spend significantly more than Labour or National on law and order.
While he says he could not work out what National was planning to spend on law and order, ACT would spend $1 billion more than Labour over 10 years on prisons, the justice system and police.