Mandate Trade Union and SIPTU members in retailer Marks & Spencer have voted to reject a Labour Court recommendation by a margin of 84% to 16%.
M&S employs approximately 2,300 workers in 17 stores nationally.
The recommendation from the Labour Court largely backed plans by M&S management for cost-cutting measures, which the unions claim would seriously deteriorate the living standards for workers at the company.
Mandate has now written to the company to invite them back into negotiations.
The union warned that any attempts to push through cost saving proposals without agreement would be resisted in the strongest possible way.
Mandate's Assistant General-Secretary, Gerry Light said, "This overwhelming rejection of the Labour Court Recommendation shows that workers in Marks & Spencer are united and prepared to fight to safeguard their conditions of employment".
Mr. Light claimed that under the company plans, some workers would be expected to take a cut of more than 20% in their terms and conditions of employment.
He added that Mandate is available to sit down to discuss issues with management.
"We have now written to management telling them that we fully expect them to respect to outcome of this ballot and ensure there will be no further unilateral actions to reduce our members’ conditions of employment. Any attempts to push through cost saving proposals without agreement will be resisted in the strongest possible way" he concluded.