Tesco says it is "disappointed" by today's action industrial action at one of its branches in Sligo.
Mandate contends its members claim they will no longer be given the right by the company to be represented by a trade union.
Tesco, however, says that this " is a local dispute involving local issues that didn’t warrant a strike."
The firm is asking the union to resume co-operation with the industrial relations processes of the State "having rejected a conciliation conference at the Workplace Relations Commission on October 24th regarding the issues in Sligo".
Tesco says "Our store remains open throughout and we thank our colleagues and the public for their co-operation."