The Ministry of Justice needs to address the huge variation around the country in Court service levels, ministry Chief Executive Andrew Bridgman says.

Writing in the ministry's Annual Report for the year to 30 June 2017, Mr Bridgeman says the length of time someone will be in the court system varies depending on the seriousness of their case and where it is being heard.

"For example, cases in Manukau spend on average 148 days in the system, whereas cases in Dunedin average 103 days. The biggest indicator of this is the adjournment rate. It will be explainable but that does not make it right. Importantly, we can do something about it," he says.

Mr Bridgman says the ministry needs to make much greater use of data and insights.

"The courts and tribunal system is a huge enterprise that has historically run without the business tools that most other systems use. If we want the rule of law to be sustained it has to be supported by good information. Otherwise, like a cottage industry or the local sports club, we will operate on anecdotes and hearsay."

Greater use of management tools and disciplines in the court system is needed, he says, along with greater use of technology. And, as a system, the participants need to be better at collaborating: "Judges, lawyers, the ministry, Police, Corrections - all of those in the system need to think about how our decisions affect others in the system, and most importantly, how effectively collaborating can improve justice outcomes for the people of New Zealand."