Beer workers at the Carling plant in Burton-on-Trent, are to hold a strike ballot later this month.
The union Unite claims more than 400 staff at Molson Coors could be sacked after June 10, and reinstated on less pay.
The union says nearly 200 workers could lose as much as £9,000 a year in wages.
More top news
Ahead of the conference, calls are growing for Midlands regions to have their own devolved powers to match those on offer to Scotland.
After a cool start, Sunday looks set to be a dry and bright day, with sunny spells.
Mainly dry with clear spells but possibly one or two light showers near coasts overnight, remaining largely dry on Sunday.