Workers at Cadbury's four chocolate factory sites have voted in favour of holding a ballot on strike action.
The closure will be phased in from 2009
Last month, the company announced it was closing its factory at Keynsham near Bristol and transferring production to Poland and Birmingham.
Staff in Keynsham, Bournville in Birmingham, Chirk in north Wales and Marlbrook in Herefordshire voted by 1,363 to 130 against the proposals.
They also voted by 1,090 to 312 for a ballot on strike action.
Cadbury's plans will mean the loss of 500 jobs at the Keynsham site by 2010.
A further 200 jobs would also be cut at the Bournville plant.
Steve Preddy, regional industrial organiser for union Unite, said its chocolate workers did not accept the decision to shut the site.
Mr Preddy said: "We felt we needed a mandate from the workforce on two elements.
"Firstly on the decision affecting the Sommerdale site (at Keynsham) and secondly whether to progress to an industrial action ballot.
"The result of this ballot reflects the anger that emanated from Sommerdale to the other sites - the proposals have unsettled the workforce."
No decision has yet been made on the length of any strike but Mr Preddy said if it came to taking action it would be "inevitable" that supplies of chocolate to the public would be hit.
Staff in Keynsham were told during an emergency meeting in October that the phased closure would begin in 2009 and be finished by 2010.
Cadbury said sites at Chirk and Marlbrook would be "unaffected" by the plans.
Unite said it would continue in talks with Cadbury and hoped to avoid any strike action.
The union will ask the company to reverse the closure decision as well as plans to restructure production and Bournville transferring work to Poland with the loss of 700 jobs in total in the UK.
Tony Bilsborough, a spokesman for Cadbury, said: "This was not a vote for industrial action and we will continue to carry out a series of consultation meetings with the unions over the next few weeks."