Unite the union has launched a campaign to halt the closure of Scottish & Newcastle's (S&N) Reading brewery and save 350 jobs.
S&N intends to close its Reading brewery by early 2010 following the announcement last year that 3m hectolitres of production would be contracted to Coors.
"S&N's decision to outsource work to a local competitor is a scandal," said Unite regional industrial organiser Mick Pollek.
"By taking away work the competitiveness of the Reading brewery has been significantly reduced.
"We can only assume that the move was designed to undermine the site - thereby preparing way for closure."
Unite is calling on the company to reverse its decision to outsource work to save the brewery.
Unite has also warned new owner Heineken of the problem and will be taking up the issue with them when they takeover ownership.
"If management do not reverse this decision then we will step up our campaign and at this stage nothing will be ruled out including industrial action," added Pollek.
"If this brewery closes it will have a devastating impact on the local economy of Reading.
"The site provides hundreds workers and their families with a decent standard of living."
Over capacity
At the time of announcing the closure Stephen Glancey, S&N group operations director, said : "It is well documented that there is general over capacity in the UK brewing sector, and these proposals have been put in place to address this issue.
"The nature of the Reading site, the amount of investment required to make it competitive and its relative cost compared to other UK facilities means that there is a strong business case for closure.
"We will, of course, do all we can to mitigate the effects of the closure on the people affected."