The system that determines wages for the Australian Defence Force's wages is "crazy" and has produced an "unhappy and unfairly treated workforce", according to one of  the nation's peak military advocacy groups.

And the federal opposition has joined in the clamour for the Abbott government to improve on its pay offer, of just 1.5 per cent per year with the loss of Christmas leave and other entitlements, to Australia's 57,000 men and women in uniform.

The Canberra Times revealed on Monday that thousands of service people had reacted furiously to the news of the offer, branding it "outrageous", "disgusting" and "a joke".

Neil James of the Australia Defence Association said on Tuesday morning that he hoped the Defence Force Remuneration Tribunal rejected the government's offer when the tribunal convenes in Canberra on Wednesday.

"Hopefully they'll reject the Commonwealth case, let's hope so," Mr James said.

"An unfairly treated and unhappy workforce is not efficient in terms of Defence capability."

The advocate said the system in place put the chief of the ADF, Air Chief Marshall Mark Binskin, in an impossible position.

"The system forces the chief of the Defence Force to act as both employer and the advocate for the employee," Mr James said.

"There is an advocate who is a supposedly independent QC appointed to represent the defence members but who isn't given the resources to do it."

Mr James said the whole system needed to be redesigned to allow the decisions to be truly independent.

"They need to come up with a way that determines ADF pay, independent of the compromising position it puts the chief of the Defence Force in," he said.

"For example, he has to choose between buying new equipment to replace obsolescent equipment or giving the troops a pay rise.

"Pay should not be determined by those types of decisions.

"Given the members of the Defence Force can't take any sort of industrial action like a strike or a go-slow, it's crazy."

Meantime, Opposition Leader Bill Shorten has weighed into the debate, calling on the Abbott government not to "short change" the service men and women.

"This will see a cut to the real wages of ADF personnel," the Labor leader said.

"This isn't fair.

"The Abbott Government should be ensuring a better deal for our ADF personnel, especially at a time when so many are deployed overseas away from their families.

"Australia asks our ADF personnel to defend our country and protect our national security – the Government has an obligation to pay them properly and give them proper leave."