Some 150 staff at a Maple Leaf factory in Walsall, which supplies own-label lines to several multiples, this week voted to strike over pay and conditions.
As many as 1,000 staff at two Park Cakes plants, which supply M&S and other retailers, are holding strike ballots this month. Brace's is consulting about making 37 staff redundant, while Hovis is planning to shed 38 in Inverness.
The Bakers Food and Allied Workers Union, which is organising the action, said companies were using the recession as an excuse to alter conditions.
Industry insiders said manufacturers would struggle to meet big pay demands because they were being squeezed by rising input costs.