Union leaders have attacked plans by the Ministry of Defence to cut a further 7,000 civilian posts as "shameful".
The Public and Commercial Services union (PCS) said it is "totally unreasonable" for the MoD to be cutting so many posts when efforts are still being made to reduce a previously announced cull of 25,000 jobs.
Officials said they had met Defence Secretary Liam Fox several times in recent months after the Government's strategic defence and security review proposed axing 25,000 civilian and 17,000 military jobs.
Staff are expected to be sent a letter from the MoD saying that further job reductions will have to be made.
PCS general secretary Mark Serwotka said cutting so many civilian and military jobs could put lives at risk, adding: "This is a shameful way to treat anybody, far less the people who serve on the front line, and those who support them.
"Since the defence review announcement in October, PCS has been thwarted at every turn in our attempts to find out where these cuts will be made and what impact it will have on the front line.
"How can the MoD announce more job cuts when they have no idea how they will run the department just now? PCS has been working on a coherent programme for defence that identifies and reduces waste, frees up service personnel to serve in the front line by civilianising non-essential military posts and eliminating unnecessary external expenditure.
"According to the MoD's own records, they spend approximately £6 billion per annum on external expenditure such as consultants."
An MoD spokesman said: "Tough decisions have had to be made to tackle the black hole in the MoD's finances. Now, for the first time in a generation, the MoD will have brought its future plans and future budget into close alignment.
"One of the measures necessary to achieve this is to further reduce civilian staff numbers by an additional 7,000, expected to begin from 2015. Much of this will be achieved through reductions in recruiting and not replacing those who leave. Compulsory redundancy programmes would be used only as a last resort."