Industrial action by workers at CityJet Handling in Dublin Airport is to be escalated next week, in a row over pay and union recognition.
A number of front desk and baggage handling staff have been on strike at the company since July and the dispute has grown increasingly bitter.
It now threatens to affect the talks on a new national partnership agreement, with SIPTU claiming yesterday that the right to union representation would have to form part of any deal.
The union's vice-president, Mr Jack O'Connor, claimed the company was denying workers their rights under the Constitution and the European Convention on Human Rights.
This was strongly denied last night by a CityJet spokesman.
Mr O'Connor said SIPTU's efforts to represent its members at CityJet for almost two years had been "hampered by a continuous supply of strike-breakers".
The company spokesman said it would be taking legal advice about Mr O'Connor's remarks.
CityJet, he said, had acted in accordance with the law at all times. Of its 145 staff, 135 had consistently opted not to have representation by a third party.
SIPTU has claimed it has 76 members in the company, but many are fearful of the repercussions of joining the industrial action.
The union said it would escalate the dispute today by picketing the offices of Manpower plc on Grafton St, Dublin, through which CityJet has recruited staff.
Mr O'Connor said the right of workers to be represented was "paramount" in the context of the partnership negotiations.
CityJet, which provides ground-handling services to a number of passenger airlines at Dublin Airport, secured a High Court injunction last month restraining a number of workers, and others, from disrupting its activities. At one stage six people were detained in custody.