Prisons could face overcrowding "chaos" because a law intended to reduce prisoner numbers was delayed by changes to the parole rules after Graeme Burton's murderous rampage.
The Criminal Justice Reform Bill is aimed at reducing the number of people in prisons by reforming the sentencing guidelines and using
home detention and community-based sentences rather than prison in more cases.
Cabinet papers reveal that officials warned at least three times that any delay to the expected April introduction of the bill would put "substantial pressure" on prisons.
However, the Government decided to add in provisions extending the non-parole periods of offenders after the public furore following parolee Burton's murder of Wainuiomata father Karl Kuchenbecker.
Cabinet papers said an April introduction of the law was essential to reduce inmate numbers in time for prisons to deal with a predicted seasonal peak in September.
However, it is still before the justice and electoral select committee, which is not due to report back until June 4. It may not become law until August or September.
The delays have drawn criticism from National Party corrections spokesman Simon Power, who said it left prisons "five months away from a potentially disastrous overcrowding situation". He said even after the committee reported back, it had to go through readings in Parliament.
"This [delay] could lead to further issues caused by overcrowding, including increased violence, problems controlling the smuggling of contraband, and even lawsuits from complaining prisoners."
A spokesman for Justice Minister Mark Burton said there was enough capacity in prisons to cope for the short to medium term, including the peak September period.
He expected the bill to become law between July and September.
Prison projections were for the prison population to increase by 1200 between 2007 and 2011. It is predicted that there will be a shortfall of more than 500 prison beds by 2009.
