SIPTU has said that a strike at Bus Éireann is now unavoidable due to what it described as the intransigence of management.
The follows last night's breakdown of talks at the Workplace Relations Commission aimed at averting industrial action over management cost-cutting proposals.
The board of Bus Éireann is expected to meet tomorrow morning to consider the financial crisis at the company following last night's breakdown of negotiations.
SIPTU Sector Organiser Willie Noone said that while every effort was made to avoid a dispute, SIPTU could not bring any plan which would slash pay and conditions to Bus Éireann members.
He claimed that union proposals would have driven out inefficiencies while simultaneously securing a decent wage for workers.
However, he said management had insisted those proposals would not bring in immediate savings.
He categorically rejected management claims that unions would try to justify "unnecessary overtime".
However, he reiterated that the union would not allow for wages earned in excess of a basic rostered week that brings what he called a "meagre" wage to a "decent" wage to be removed by management without agreement.
He said Bus Éireann had proposed that some drivers would drive considerably more hours and retain traditional payments - but that others would not have same opportunity, resulting in a pay cut.
Mr Noone also claimed that the company had refused to support a strict time bound process to eliminate inefficiencies.
He said management wanted to eradicate inefficiencies almost immediately, which would result in "savage" pay cuts for workers, with changes imposed inequitably.
He also criticised management for failing to supply adequate detail regarding the impact and implementation of the proposed changes.
The General Secretary of the National Bus and Rail Union has said at the eleventh hour Bus Éireann management insisted on a cut to take-home pay for drivers.
Dermot O'Leary said unions were committed to talks engaging on efficiencies, adding that overtime was not a luxury but part of a take-home salary.
Mr O'Leary said there was plenty of scope to achieve cuts of €9m across the company.
He said if the company tried to unilaterally introduce cuts, it would lead to a dispute situation and all strike action would be reactivated on the same day.
"If they announce changes on a given day, all the unions will reactivate our strike action on that day.
I want to be very clear that we're prepared, even at this stage, to go in and discuss efficiencies and embrace that agenda.
"We've said this from the very start and we're quite prepared to do that."