Civilian staff employed by the Defence Force (NZDF) have started industrial action after being offered no pay increase, with more jobs set to go.
The Public Service Association says staff were told on Thursday a major restructure would "likely result in a further reduction in the civilian workforce to meet funding pressures".
National secretary Duane Leo said NZDF had already accepted about 200 voluntary redundancies - about 8 percent of its civilian workforce.
"There is nothing more frontline than the defence of the nation, so this decision is just more evidence of the government's reckless and short-sighted approach to cost cutting," he said.
The announcement of further cuts pending followed NZDF's decision not to offer any pay increases during bargaining for a new collective agreement.
PSA members started six weeks of work-to-rule industrial action at 9am on Wednesday, set to last until 5pm on 31 October.
Members at Kauri Point in Auckland have deferred the start of their industrial action until 2 October, as they were required to give 14 days' notice because the loading and unloading of ships was considered "an essential service".
Leo said the government should be funding NZDF "properly" at a time of rising security threats in the Pacific.
"The threat of further job cuts just rubs salt into the wounds of an already stretched civilian workforce with many staff dealing with double their usual workload.
"They do such vital work supporting the men and women in uniform across all branches of NZDF, here and overseas. To further reduce the number of civilian workers will add just cause more stress. It's a recipe for disaster.
"Our members are just gobsmacked that their roles should be so disrespected by NZDF. We urge the government to rethink this irresponsible approach to saving money."
NZDF has been approached for comment.