Labour Party leader Chris Hipkins is opposed to the ACT Party's proposal to increase the size of the prison population.
ACT wants to add more than 2000 prison beds by 2027, increasing incarceration to levels last seen in 2017.
The Labour government has worked to reduce the size of the prison population.
Chris Hipkins said he was not interested in increasing prison numbers, but he was open to reviewing electronic monitoring devices.
ACT leader David Seymour said to a large extent additional prisoners could be accommodated in existing facilities where staffing levels had been run down.
But he did acknowledge that a new prison might be needed, but said that would be for Corrections to determine.
Hipkins has been out on the campaign trail in Auckland today, while National leader Christopher Luxon was campaigning in Whanganui this morning.
Recap Saturday's developments on the campaign trail with RNZ's blog here:
