About 40 naval engineers, architects and other technicians will refuse to work on the subs program for a week from midnight on Tuesday, and will also target the future frigate program, the offshore patrol boat program and the replacement of a vital naval refuelling vessel.

Fairfax Media revealed this month that the Department of Defence was down to just just one in-house naval architect working on developing the new subs as well as the task of keeping the existing fleet afloat, and he is understood to be planning to join colleagues on strike on Wednesday.

The technicians' union says its members are protesting about what they say is a gradual degradation of the Defence Department's technical workforce, describing those who are left on the job as "the thin grey line".

The union, Professionals Australia, says the dwindling resources of in-house technical expertise at Defence put lives in danger at sea and on land.

The Department of Defence did not respond before deadline on Tuesday to a request for comment.

Specifically, the strike action is a week-long ban on "technical and engineering work or tasks relating to the offshore patrol vessel project ... the future frigate project ... the auxiliary oiler replacement project [and] naval architecture work or tasks relating to the future submarine project."

The technicians from the Navy Technical Bureau and the Defence Acquisition and Sustainability Group want their long-standing grievances about the strength of their workforce addressed as part of the marathon enterprise bargaining process at Defence, a call they say has so far been rebuffed by their bosses.

Union official Dave Smith said Defence's technical know-how had now been neglected and run down to a level where lives were at risk.

"Our members play a critical role in bringing engineering expertise to the acquisition and maintenance of complex, high-risk technology," Mr Smith said.

"They have become a thin grey line – the state of the engineering and technical workforce is a risk to this capability, and hence to ADF lives."

Mr Smith said the bargaining talks so far were looking likely to make the situation worse.

"The agreement process provided an opportunity to address some of these issues but instead it has made them worse – and harder to retain critical expertise," he said.

"That's why Professionals Australia members are taking action in relation to the future frigates, patrol boats and submarines program to highlight these problems.

"Defence seems to be oblivious to the dangers of outsourcing to contractors, the consequences of cuts to manpower and resources, the dilution of risk management processes and an over–reliance on the tired few who each year get fewer," he said.

"Defence has learnt nothing since the decommissioning of the Kanimbla and Manoora, with the Department refusing to address engineering issues. They are sleepwalking into a bigger disaster and our members are trying to wake them up.

"They are putting lives at risk as well as billions of dollars."