The National Bus and Rail Union (NBRU) say the threat to Bus Éireann expressway services cannot go unanswered by the Government.
General Secretary Dermot O'Leary has criticized Minister Shane Ross for not engaging with them.
The NBRU were before the Oireachtas Transport Committee earlier to discuss controversial plans for the restructuring of the Bus Éireann expressway service.
The union's Dermot O'Leary said the people of rural Ireland would not stand for the cutting of their bus services, and the Minister needed to engage.
In a statement, the union said: "The notion that an unchecked toxic policy...can be allowed to arbitrarily undermine the social and economic fabric of hundreds of communities by disabling Bus Éireann’s ability to serve these areas is simply untenable and politically questionable."
Mr O'Leary added: "The Minister (Shane Ross) has not met this trade union," he said. "I've written to him on three occasions and briefed him in June which forewarned him of the Bus Éireann situation," he said.