Staff at Dunnes Stores are to ballot for industrial action.
The retailer employs more than 10,000 workers in 112 stores in the Republic.
The Mandate trade union, which represents more than 4,000 of the staff, says the ballot is taking place after the company refused to implement the terms of a Labour Court recommendation issued last November.
"Many of our members cannot access mortgages or loans because of insecurity of hours due to low-hour contracts," said Mandate Assistant General Secretary Gerry Light.
"Dunnes workers want to have their right to trade union representation vindicated, particularly when it comes to disciplineries and collective bargaining."
The balloting process will commence in the coming weeks.