Strike action across Cadbury's UK factories moved a step closer this week after workers voted "overwhelmingly" in favour of industrial action in a preliminary ballot.

Unite union officials said workers could down tools within weeks after they voted eight to one in favour of a strike ballot. Turnout was reported to be over 75%.

The union is now taking legal steps toward holding a formal ballot and will release a timetable later this week.

Cadbury is locked in a dispute with the union over a three-year wage deal. Unite national officer for food and retail Jennie Formby said the deal, agreed last year, committed Cadbury to giving workers retail price inflation plus 0.5%, with a minimum raise of 2% and a maximum of 5%. She accused Cadbury of reneging on the deal, as the company has offered workers a 0.5% rise this year.

"Cadbury is a tremendously wealthy company and our workers work hard to generate its profits," she said. "Todd Stitzer and the other executives receive great pay and bonuses and it's only reasonable that Cadbury's workers get a fair deal too. Unless Cadbury comes back to the table, it could face strikes across the country in a matter of weeks."

Unite said Cadbury's factories, especially its main facility in Bournville, were heavily unionised and any industrial action would have a "significant" impact on Cadbury's output.

Workers at the Cadbury Somerdale factory, which is scheduled to close when production is shifted to Poland, will not join the strike action if it goes ahead, Formby said, as their redundancy settlements would be jeopardised. Instead, they will show their support through demonstrations and other action.

A Cadbury spokesman said: "We have said all along that we have kept to our three-year pay deal and, in the light of current pay freezes for all other Cadbury employees, this increase is fair, particularly given current economic conditions. It's vital we stay competitive if we are to remain successful."