The trade union Siptu has begun a campaign to highlight what it says is the threat to employment standards from the proposed EU Services Directive.
Speaking at a seminar in Dublin, Siptu general president Jack O'Connor said there was an urgent need for "serious public debate" on the planned directive.
He claimed that in its current form, the proposal would "legitimise the erosion of wages and working conditions".
The directive would allow companies provide services in any EU member state without being subject to local labour regulations.
Mr O'Connor said although he acknowledged the rationale for a measure to overcome regulatory obstacles to the internal market for services, he would question the justification for the measure currently proposed.
"Instead of helping the new accession states raise the productivity, working conditions and living standards of citizens to the highest possible level, as Ireland was helped in the past, the lowest common denominator will be called into play. Conditions will be driven down to the lowest levels."
He said economic analysts had told the European Commission that the savings achieved would be worth "less than 1 per cent in the majority of traded services", while the effect it had on living standards and working conditions for thousands of EU citizens would be "devastating".
The Siptu president said an amendment being considered to provide for compliance with labour law in the host country would do nothing to protect employment standards in Ireland because they are set through collective bargaining.
Mr O'Connor said all the amendment would do was to ensure payment of the national minimum wage, which is just half the average industrial wage.
The Austrian presidency of the EU said on Monday it would make the directive a priority. It is expected that a draft will be available by March.
Speakers at the seminar, which was organised by Siptu as part of its public awareness campaign on the EU directive, included Minister of State Tom Kitt, Labour MEP Proinsias De Rossa, and a number of party spokespersons on trade and enterprise.
Mr De Rossa welcomed an admission this week by European Commission president Jose Manuel Barosso that the services directive had to be fundamentally rewritten.
"In going over Commissioner McCreevy's head in this way, President Barosso has finally acknowledged that the EU cannot rip open the services sector in member states in the way proposed without deepening concern amongst citizens about a lemming-like race to the bottom in labour, consumer and environmental standards and in public service provision," he said.