Civilian technical officers at two RAAF air bases, a Navy airfield and an explosives testing range walked off the job on Monday, protesting against what they called the government's "draconian bargaining policies".

The department has played down the impact of the actions, saying that only four workers took part in the stop-works but their union says each of the technicians plays a vital safety roles in already diminished Defence workforce.

The department will sit down with unions next week to continue its wage talks, nearly 2½ years since its public servants last had a pay rise.

The technicians, members of the Australian Manufacturing Workers Union, walked off their jobs for 24 hours at RAAF Base Williamtown, RAAF Base Richmond, HMAS Albatross in Nowra, and Defence Establishment Orchard Hills.

The Navy base at Nowra, where training and operational flights are conducted, was temporarily shut down in 2014 amid concerns the lack of technicians working there had become a safety risk.

The union is unhappy that only six of the technical maintenance jobs are filled by experienced workers with the gaps filled in by shifting Defence Force personnel from around NSW.

But it is the ongoing pay dispute that sparked the strikes, which were protected under the Fair Work Act, AMWU assistant national secretary Mike Nicolaides​ said.

The union official acknowledged that the numbers involved were small, but said their safety-critical roles meant the impact could be serious for Defence Force Operations.

"The technical workforce in Defence is being run down, so there's not a lot of them and some of them are members of other unions," Mr Nicolaides said.

"They [the technical officers] maintain the navigational aids and if the navigational aids go down, the facility becomes non-operational."

"They're in critical positions."

"These people are required to give five days notice of industrial action instead of the normal three because they are in safety-critical areas.

"Because of that, we have been reluctant for them to take industrial action, and the industrial action that we have taken has been done on far greater notice, so we've given Defence sufficient notice so they can make alternative arrangements."

"Now of course that's inconvenient, but we don't want to threaten safety."

A Defence Department spokeswoman said the impact of the strike action had been "minimal".

"At the time of this advice four employees have been reported as participating in the notified industrial action," she said.

"Industrial action has had minimal impact on operations."

The Defence Department will sit down this week with unions to talk more about the wage offer, of 3 per cent in the first year followed by 2 per cent and 1 per cent, with the civilian workforce still deeply unhappy about cuts to conditions to entitlements that come along with the offer.

There is also lingering resentment over the big concessions made to their colleagues in the Australian Defence Force after a political backlash last year.

Mr Nicolaides said more industrial action from members of his union working in the sprawling Defence establishment was likely but the nature of the actions might vary widely from between different bases.

"Each of these Defence establishments is basically different from the next in term of funding, the level of union membership and other things."

"It's dependent on the circumstances of each site, whether something will happen and that will vary from site to site."