Technical union Professionals Australia says it wants public servants and their military colleagues to "redeploy your lanyard" to highlight the workplace discontent at the giant department.

The union is providing pre-paid envelopes to Defence staffers to send their old lanyards to departmental secretary Dennis Richardson or Defence Minister Kevin Andrews to register their unhappiness.

Defence is drastically downsizing, with PA saying that vital technical and engineering expertise is walking out the door.

The department's negotiations for a new three-year pay deal are locked in stalemate with the workforce rejecting the offer on the table but bosses saying they cannot afford to offer more.

Defence is also embarking on its biggest structural shake-up in decades after its First Principles Review and bosses sent out the message last week that one of the first items on the agenda was to get everyone wearing the same lanyard.

Professionals Australia official Dave Smith said he launched his protest because focusing on lanyards and acronyms sent the wrong message to workers in a department facing big challenges.

"Defence has real challenges and the main one is its people," Mr Smith said.

"Not the superficial ones such as the move to one lanyard or to change all the Defence organisational acronyms.

"They're the kind of moves that we suspect some consultants have probably been paid too much for, and will waste millions of dollars while not addressing the real challenges for Defence."

The union says its "redeploy your lanyard" section on its website was already striking a chord with workers in the department.

"Employees deciding to redeploy their lanyard have the opportunity to send the minister and secretary a message that they want them to focus on the real issues not the trite ones," Mr Smith said.

"At the same time we can save the department millions of dollars by getting staff to redeploy their lanyard and get a Professionals Australia one for free, rather than the proposed one defence lanyard."