Plans for a £20m expansion of the Royal Mail centre at Swindon could see job losses in Gloucester and Reading.
Bosses said job losses would be achieved by voluntary redundancy
Under the plans, mail centre operations at Reading and Gloucester would move to the expanded Swindon site at Rowland Hill Close, Dorcan.
A Royal Mail spokesman said the move would allow outdated buildings to be replaced and new technology introduced.
Plans will now be submitted to Swindon Borough Council. If approved the new offices could open by 2008.
It is not yet known how many people will be employed at each of the locations under the new structure, but Royal Mail believes job losses would be largely achieved by natural wastage and voluntary redundancy.
Shaun Chute, from Longlevens, is one of the workers at the Eastern Avenue sorting office in Gloucester. He was told of the plans at a meeting on Tuesday night.
"The management got us all into one place and told us. We knew something was up when they told us to gather round.
"I'm very disappointed and there was a lot of disbelief. It's going to take a bit of time to sink in," he said.