The Defence Force says up to 52 jobs will be lost amid restructuring at Devonport Dockyard.
Staff have today been told about the restructuring, which would also see a private contractor create 46 new positions.
The Defence Force said some of the 52 workers will be redeployed.
Public Service Association's (PSA) national secretary, Richard Wagstaff said privatisation was a bad move as it would mean a loss of experience and knowledge.
"There's a sense that people put their careers, so much time and effort and commitment and loyalty into a job and when that job doesn't show that loyalty back it hurts."
Defence shake-up 'complete shambles'
The Defence Force blamed what it called an "unexpected process issue" for postponing the announcement about the job restructuring at the last minute.
About 200 civilian and military Devonport dockyard workers gathered at a meeting yesterday, expecting to learn their fate following a proposal that would see jobs cut.
Mr Wagstaff said the workers were then told by management the meeting would not be going ahead.
"A couple of hundred workers turned up to the meeting and the Defence Force says, sorry, we can't have the meeting, which is a very difficult thing for those staff to have to go through."
Mr Wagstaff said they had not received any explanation as to why the announcement was canned, and said an apology should be made.
"We don't expect them to change their plans but we can't explain why it is that they would call people in, only to tell them that they can't tell them anything," he said.
"It seems like a complete shambles."
In a written statement yesterday, a Defence Force spokesperson said something unexpected cropped up.
"Unfortunately, we were unable to share the outcomes due to an unexpected process issue.
"We made every effort to resolve it in time to hold the meeting as planned, but it was not possible.
"The matter was resolved this afternoon.
"We regret the delay and apologise to the dockyard staff for the inconvenience it has caused them."
A spokesperson for the Minister of Defence's office said it was an employment matter and no comment would be made.