In a move likely to prolong the Ryanair dispute involving ground handling staff at Dublin airport, the company has declined an invitation to attend the Labour Court, which had called both sides to a hearing.
Mr Paul O'Sullivan, a SIPTU negotiator, said the stance "presents very serious questions for the Government when a publicly quoted company can ignore or try to ignore an institution of State".
SIPTU would be attending the Labour Court on Friday, he said. It believed that, in not attending, Ryanair "seemed to have something to fear from the court's investigation" of issues including low pay and health and security for its workers.
The union had said it was prepared to consider deferring escalation if the company agreed to attend.
The Minister of State for Labour, Trade and Consumer Affairs, Mr Tom Kitt, said he was disappointed by the company's response. He had encouraged the use of labour-relations machinery and remained convinced that "dialogue mediated by a third party" could assist in clarifying issues and contribute to a solution.
In a letter to Ms Evelyn Owens, chairwoman of the Labour Court, the Ryanair chief executive, Mr Michael O'Leary, said since the company had not requested the Labour Relations Commission nor the Labour Court to investigate or intervene in the action "of a tiny minority of our ground operations people", it would not be accepting the invitation.
The company strongly believed the intervention would "only prolong the misleading and failed media campaign being waged by SIPTU and detract from the calm, ongoing dialogue being conducted within Ryanair with both the 97 per cent of our 954 people who are working normally, and the minority engaged in limited work stoppages".
In a statement, Ryanair said its policy throughout was to refrain from media comment because of direct talks with its staff. As the Labour Court announced its proposed intervention by way of press release, it had taken the liberty of releasing a copy of its reply. It would, however, not be commenting further.
The Democratic Left leader, Mr Proinsias De Rossa, said the rejection left the Government with no option but to exert "all possible pressure" on Ryanair to recognise the right of its workers to be represented by a trade union.
