The government is being urged to hurry up and commit to urgent upgrades of old and risky Defence Force property.

Photo: RNZ / Richard Tindiller

Today, RNZ has reported on a scathing briefing to the Defence Minister, Ron Mark, last September.

It showed 41 percent of the estate - that's camps, buildings, roads and water infrastructure - falls short of, or barely meets, functional requirements.

The document showed barracks at Burnham, Ōhakea, Waiouru and Trentham urgently need investment.

More than 300 buildings were near the end of their operating life, and 47 are potentially earthquake-prone.

Overall, it said 78 percent of the defence force estate needed to be replaced in the next 30 years.

National's defence spokesperson Mark Mitchell said the military had a good knack of maintaining old property.

He wanted Mr Mark to publicly state his plan for repairs and maintenance.

"He [Mr Mark] keeps reviewing everything, I think it is a delay tactic - he just needs to stump up [and] restate his commitment to our plan," Mr Mitchell said.

"If he's going to bring that forward then say clearly what he intends to do and how much money it is going to take."

Photo: RNZ / Richard Tindiller

Mr Mark announced last year $2.3 billion would be spent replacing the old Orion planes with new P8 Poseidons.

Green party defence spokesperson Golriz Ghahraman said she was alarmed to hear about the extent of the outdated estate.

She would have preferred to have seen the P8 money spent on infrastructure upgrades.

"I wouldn't have, as I've said, I wouldn't have invested in the planes last year - which were mostly costly because they have war-making technology on them and we could have gotten on with this," Ms Ghahraman said.

Defence expert Robert Ayson from Victoria University has seen first-hand how dated some of the assets are.

He said when planning for upgrades, Mr Mark may go for quality over quantity, to reflect a modern military.

"If you ask the Defence Force - 'do they need all of the facilities, all of the infrastructure, all of the buildings they currently have - including barracks?' The answer would probably be no.

"The Defence Force would probably be better suited by a smaller number of buildings - in particular - but updated ones," he said.

In a statement, Mr Mark said the previous government didn't appropriate all the $1.7b upfront for upgrades.

He said he was assessing the needs of the Defence Force estate and he would not rush into it blindly.

Mr Mark said he needed to be sure the investment was smart and future-proofed.