Corrections staff say Judith Collins' clamp on bail is keeping more inmates in jail.
Corrections officials say the prison population has unexpectedly risen this year, and they believe one of the causes is hardline bail laws introduced by Judith Collins when she was Justice Minister.
The total number of inmates in New Zealand's 17 prisons had been forecast to steadily decrease between 2010 and 2016 as a result of a falling crime rate, increased use of community sentencing, and a stronger focus on reducing reoffending.
But in a briefing to new Corrections Minister Sam Lotu-Iiga published this week, Corrections officials said: "While these forecasts were reasonably accurate up to the end of last year, the current year has featured an unexpected climb in prison numbers, particularly affecting the remand population."
The briefing paper said the prison population was about 8700 people, up from 8500 this time last year.
Two factors were identified as contributing to the larger population -- a small increase in violence and Class A drug offences, and a law change in October last year that made it harder for people facing murder charges or repeat violence, sex or drugs charges to get bail.
Mrs Collins' law change reversed the burden of proof for accused offenders in bail cases, and was expected to lead to 350 more people a year being refused bail.
The National-led Government does not have a specific goal for reducing the prison population. But it wants to reduce reoffending by 25 per cent between 2011 and 2017, which should lead to fewer people being locked up.
The Government has estimated that if it reaches its reoffending target there will be 600 fewer people in prisons than in 2011, meaning the prison population would be around 7950 in 2017.
Mr Lotu-Iiga said the growth in prisoner numbers was not a cause for concern "at this stage" and was unlikely to affect planning or policy.
• Sept 2010 - 8,747
• Sept 2011 - 8,488
• Sept 2012 - 8,623
• Sept 2013 - 8,474
• Sept 2014 - 8,700 (estimate)
- Source: Corrections NZ