Siptu general president Jack O'Connor has appealed for a huge turnout for Thursday's march to the Dáil and described the Irish Ferries dispute as the "harbinger of the future".
The march is in protest against the proposed EU services directive.
It would allow employers "to transport workers from one end of the EU to the other and impose the 'going rate' in the member state with the poorest conditions applicable", Mr O'Connor said.
The leader of the country's largest union has called for a "fundamental change in our present social partnership model so that social objectives are at least given parity with economic growth".
The Irish Ferries situation was the "threat that is looming" for workers and their families if the social partnership model does not change.
The dispute was symptomatic of a trend where workers on agreed national terms of employment were being replaced by migrant workers on half the rate of pay.
Irish Ferries had become significant because "it is the highest profile and most blatant example of that trend".
He warned that "concern is no longer enough. People must mobilise".
"Irish Ferries is a harbinger of the workplace of the future. The same blind market forces that are driving down pay and conditions there are coming closer to everyone's workplace."
Irish Ferries "is providing us with a glimpse of the future labour market if neo-liberal zealots succeed in pushing through their services directive".
This "was a complete repudiation of the European social model in the name of greed", he said.
"If the services directive is adopted in its present form it will reverse this process and, instead of the EU serving as a means of bringing living and working standards up to the highest levels prevailing across the continent, everyone will be dragged down to the lowest rung.
He said that "what is happening in Irish Ferries provides a glimpse of the neo-liberal nightmare towards which we are currently drifting".
Mr O'Connor added: "We have to ensure it remains just a glimpse, and that EU policy makers steer a saner course that reinstates the social values at the heart of the European model."
