Sinn Fein has called on the management at a plant that treats water for a quarter of a million people in Dublin and Wicklow to stop using strike breakers and to get back around the talks table.
SIPTU workers from Shanganagh waste near Bray have downed tools in a row over changes to pay and conditions.
They said that things have now “escalated” because the company have brought in staff from Spain.
Senator David Cullinane has called on the company to talk to their staff and end the strike.
"We're making a direct appeal to the management of the company to recognise that what they are doing is counter-productive ," he said.
"They need to properly and fairly negotiate with the workers, end this unfair practice of bringing in strike breakers, deal with the grievances that the workers have and accept the industrial relations machinery of this state is the mechanism they should use to resolve these issues."