The Royal Mail sorting office in Ipswich is set to close by the summer of 2015, staff have been told.

The company – which is preparing for privatisation – has told staff that 139 sorting office jobs will be affected when all sorting currently undertaken in Ipswich is moved to Chelmsford.

Ipswich staff are now being balloted on possible industrial action in response to the closure threat – the result of the ballot is due to be announced on September 16.

A spokeswoman for Royal Mail said that the consultation on the future of the Ipswich sorting office, which started in November last year, was continuing.

However the current thinking of the company was that it would start winding down sorting operations in Ipswich next autumn and all sorting would transfer to Chelmsford by the summer of 2015.

The sorting office is owned by the borough council – and leader David Ellesmere was disappointed to hear about the current proposals: “There would be a loss of jobs from Ipswich. Even if some people transferred to Chelmsford, when they came to leave the jobs would be filled by people from Essex – they will be lost to Ipswich.”

Dave Scott, the local secretary of the Communications Workers said staff were angry at the proposed closure of the sorting office – and he felt many would be unable to transfer.

“Some of the staff there are part-time, working 15 hours a week. It isn’t going to be viable for them to go down to Chelmsford.

“This is very bad news for Ipswich and the Royal Mail in particular – but we feel this was always what was going to happen.

“They said they were having a consultation, but they always knew what result they were looking for.”

The Royal Mail said that in previous sorting office closures a significant number of staff had transferred to new locations – although the spokeswoman said they accepted this was not always possible.

She said the proposals should not affect mail delivery or the collection of parcels which should continue from the existing building in Commercial Road.

“But I have to stress that this is only our current thinking – we are still talking to unions, staff and other interested parties and we have not reached any final decision.”