"The current operating model (with fixed numbers of police, and a nation-wide network of courts and prisons) is likely to cost at least $140 million more than current baselines by 2017/18. Sustaining an effective and trusted justice system requires a level of baseline funding that is now under considerable pressure."
The briefing also says that, Courts and Police, allowing for inflation had experience cuts in funding of 7 per cent and 3 per cent since 2010.
Earlier this year after the Government sliced a little more off their funding in the last Budget, Police officers warned "something will break" if their funding was squeezed any further.
Total spending on police fell slightly from $1.5 billion to $1.46 billion in 2014/15, meaning it has barely risen in five years.
Also redacted from the document was a recommendation to extend Youth Court jurisdiction to 17 year olds.
Currently Youth Court deals with offenders between 12 and 16.
The briefing sets challenges for maintaining trust and confidence in the justice system including "Effective responses for 17 year olds".
"Currently the adult criminal jurisdiction begins at 17, which is out of step with comparable jurisdictions and international legal obligations. Evidence suggests better long term justice outcomes (reduced lifetime offending) and social and economic outcomes (improved skills and employment prospects) could be achieved by dealing with 17 year olds in a different way to adults," the briefing says.
A spokesman for Justice Minister Amy Adams confirmed she had made the redactions in consultation with officials, "a per normal OIA procedures".
He said Ms Adams "hasn't formed a view on specific policy addressed in the BIM, which is why it was redacted".
"Simply, no final decisions have been made".
Labour justice spokesman Andrew Little said the funding pressures revealed in the briefing were unsurprising.
"The last six years has been all about driving down cost in the justice system but the reality is when you talk to lawyers working in any part of the court system they'll tell you that there are difficulties, backlogs and too few staff to process applications and the like. I think the entire justice system is under huge pressure."
Mr Little also criticised the use of the Official Information Act as grounds to withhold sections of the briefing.
"It's not meant to prevent embarrassing information coming out it 's meant to protect the free and frank information to ministers."
He believed the material had been redacted from the briefing because the Government was "embarrassed that they're going to have the public seeing that someone in the bureaucracy actually accepts that there are real pressures in the justice system now because of funding".
"That's not a reason to withhold it and I think it certainly warrants attention from the Ombudsman."
He believed the recommendation around extending the youth justice regime was uncontroversial and shouldn't have been redacted.
"There has been pressure on for some time to do that and I think that is warranted."
Mr Little said 17 years were still only on the cusp of adulthood, "and if you can prevent them from going into the hard end of the justice system that is better than processing them as an adult."
Diane White, a spokeswoman for youth justice reform group JustSpeak said her organisation was "thrilled" with the advice to Ms Adams around 17 year olds.
"We have long been campaigning for this change, as we see the youth justice system far better equipped to deal with 17-year-olds than the adult system. The system has proven better outcomes for both victims and offenders, and having done the maths we believe it's a wise investment and in line with the Government's overall goal to reduce reoffending.
"This would bring us into line with our international obligations. The fact 17-year-olds are currently subject to the adult criminal justice system has seen New Zealand criticised in the international arena, and an outlier amongst comparable jurisdictions."