Oxford's main sorting office, the Oxford Mail Centre, is to close in 2009 as part of a £20m expansion plan for the Royal Mail centre in Swindon.

It was announced 12 months ago that operations at Reading and Gloucester would be moved to Swindon, but the announcement regarding the closure of Oxford's mail centre came as a shock to postal workers in Oxford last night.

One bemused postal worker who contacted the Oxford Mail said the switch will mean that, from 2009, all Oxford mail will have to travel from Swindon each night before it reaches the county's delivery offices.

More than 430 staff work at the mail centre at Oxford Business Park, and members of the Communication Workers Union were this morning considering the implications of the closure.

Oxfordshire's CWU spokesman Bob Cullen said: "Obviously we are very hostile towards this decision and see it as an attack on the branch - there is no logic to it.

"It is going to lead to an inferior quality of service for the Oxfordshire public with their mail arriving later.

"There was no notice or consultation over this - even the mail centre managers did not know and they were breaking down in tears last night. I don't think any jobs will go and we are going to fight the closure."

The new plan means Oxford and Reading mail centres will now close in 2009, but Gloucester will remain open.

Royal Mail said the changes addressed "an urgent need to improve mail consistency and efficiency".

Area general manager Michael Devanny said: "We believe that moving work from Oxford to our extended facility in Swindon, which will be equipped with the latest technologies, will enable us to address an urgent need to improve the reliability of the mail services for our customers in the OX postcode area.

"Our first priority as we take forward this plan will be to fully support staff at all sites, particularly recognising the impact on our Oxford colleagues as a result of the revisions to our original proposals.

"Royal Mail would put into place a very positive support package to help its people through any period of change.

"Royal Mail has an excellent track record of managing people through change, and we will consult with the unions and our employees in the coming weeks and months to help them through this difficult time.

"The timescale for development of the extended Swindon Mail Centre will mean a full transfer of work from Oxford and Reading Mail Centres by early 2009.

"Development work is due to start at Swindon October 8 and, once complete, the mail centre will be the largest, most state-of-the-art in the country."

Last week, the CWU in Oxford balloted for strike action after suspended worker Steven Gill, at the centre of a five-day wildcat walkout last July, was allegedly dismissed.