Top ministers have ordered a "deep dive" into the Defence Force's spending in a bid to free up more funding to "lift the wellbeing of New Zealanders".

A document obtained under the Official Information Act shows Treasury and the Defence Ministry have been instructed to free up what's deemed to be less-important spending.

Finance Minister Grant Robertson said the cost-cutting exercise would focus on projects which aren't delivering.

The Opposition is critical of the Government plan, as it comes at a time of "heightened global instability".

The idea would be to make it available to other government areas, in a bid to lift the wellbeing of New Zealanders.

Massey University lecturer David Belgrave told Mike Hosking it's not indicative of this Government's views on the military.

"Squeezing a bit of money out of day-to-day spending is quite different from the billions of dollars they are going to need to spend upgrading military equipment over the next ten years." 

He says we need to know how much funding will be cut, before we worry.

"If we started to deferring the major upgrades we need to spend, especially on the aircraft and the navy, then I think our security partners would start to be concerned."