UK unions have slammed Cadbury Schweppes' decision to press ahead with plans to close its Keynsham chocolate factory.

The world's largest confectioner is set to close the site under plans first announced in October, despite fierce local and union opposition. Some 500 workers will be affected by the move.

Union officials put forward alternative plans for the site but Cadbury remained unmoved. Brian Revell, national organiser for food and agriculture at the Unite union, claimed that Cadbury's move would help create an "industrial desert".

"This is a disgraceful decision," Revell said. "Cadbury managers have failed to address the real business and environmental arguments we put forward and, what is worse, if the rest of the country followed their perverse and ill-informed logic, Britain would be an industrial desert."

He added: "After a lengthy consultation the best Cadbury managers could come up with were half-baked excuses. If the Somerdale closure goes ahead, Cadbury will be adding 12m food miles to their brands. That should send a powerful 'don't buy' message to all Cadbury consumers."

Cadbury said the alternative plan put forward by the union "would simply not have allowed us to remain competitive".

The company's UK managing director Trevor Bond added: "We appreciate the union's attempt to put forward an alternative proposal and we looked at the business case at length. It was a difficult decision but it simply wouldn't have allowed us to reduce our costs to a level at which we could compete effectively with companies such as Mars and Nestle."

Cadbury's plans to restructure its UK business are part of a wider overhaul of its operations worldwide in a bid to drive efficiency and boost margins.

In the UK, Cadbury also plans to shift some of its production of chocolate assortments from its flagship Bournville site to Poland, a decision that will see 200 workers lose their jobs.

Nevertheless, Cadbury said that the restructuring would see the Bournville facility get some GBP40m (US$78.7m) of investment as chocolate production switches from Keynsham to the Midlands site.