Unions representing Dunnes Stores workers said they have been threatened with redundancies if they choose to strike.
The result of a ballot on industrial action is due to be announced this afternoon.
The row centres around pay and conditions at the retail chain, with the Mandate union saying management has refused to engage with them on the issues.
"It's a very difficult situation for many of our members … they work, very many of them, in a very hostile work environment," said Gerry Light, Mandate's Assistant General Secretary.
"Three weeks ago, management wrote to each individual worker, clearly stating that in the event of industrial action taking place, it would inevitably lead to layoffs and redundancies."