Depot workers for Sainsbury's have been balloted on possible Christmas strike action in Merseyside.
The 800 staff at the depot in Haydock were voting on Thursday as part of their demands for a wage increase to match the regional average.
Shopworkers' union Usdaw said its members are angry they are being paid £5.75 an hour, despite the fact workers are earning an average of £8 an hour in the region.
Sainsbury's said it is currently in negotiation with the workers and hopes to reach an "amicable agreement".
'Reneged on promises'
However, Usdaw area organiser, Glen Dyson, said: "The feedback
from the shop floor is that our members are very angry.
"They feel the company has made promises and then reneged on them."
Results of the vote are expected to be announced on Friday and if the offer is rejected strike action is likely to take place on or around 22 December.
The Haydock depot supplies Sainsbury's stores across northern England.
A Sainsbury's spokeswoman said: "We're currently in discussions with
colleagues at the Haydock depot to prevent industrial action and are hopeful
that we will reach an amicable agreement imminently."