Workers at Dunnes Stores who are members of the Mandate trade union have voted in favour of industrial action in a row over pay and conditions.
Mandate is accusing the retailer of using low-hour contracts, and is seeking improved security of hours and earnings for staff.
More than 5,000 Mandate members were asked to ballot - the union says just over 3,000 took part in the vote.
67% of union members balloted voted to take industrial action.
The Labour Court has recommended that the company engage with unions to discuss the issues in dispute, but in a letter to its 14,000 staff last month, Dunnes said it had a constitutional right not to engage with unions.
It also warned workers they could face redundancy if they go on strike.
Dunnes Stores said it had put in place two pay rises and maintained employment levels despite the challenging economic environment.
Gerry Light, Assistant General Secretary at Mandate, described the outcome of the vote as "remarkable".
Mr Light said the majority voted in favour because of their job uncertainty and the precarious environment they have to endure.
"Principally the issue we are trying to deal with is all around decency and about guaranteed earnings.
"What that means is that from one week to the next a Dunnes Stores worker should know what their earnings are going to be.
"That should not be too much to ask in this day and age."
He said any attempts to negotiate with Dunnes Stores up until now has been ignored.
"We have been attempting to deal with these issues for least 18 months with Dunnes Stores, but unfortunately they just ignore us, they won't come to the negotiating table.
"They ignored us last November when an LRC recommendation clearly stated that they should come to the negotiating table to discuss these issues", he said.
