However, Mr Nash said it was hard to understand why the budgets were underspent when crimes like burglary were being neglected.
"I'm concerned about the overall police budget. I think it needs to be bigger, but it's hard to make a case for more money when you've got seven districts under-spending."
Police Association President Greg O'Connor said the underspend in the districts arose from a "climate of fear" about spending.
"There will be a lot of very disappointed police staff, particularly middle managers who have been turned down for operations and equipment, who have been told they couldn't run those operations and now they are told there is money left over."
Money was only spent in policing when it started hurting politically, he said. "Now burglaries are going to start hurting the Government, there will be hopefully now some investment in that area."
A police spokeswoman said: "Police ... proactively manage their resources across all of New Zealand to maximise delivery of policing services to the New Zealand public. This frequently leads to minor variations in expenditure between appropriation classes, which are driven by operational demands."
Ms Collins said she had given police a "firm message" to focus on increasing resolution rates.
Morgan Tait