Striking bus drivers have vowed to ground the Bus Eireann fleet for a second day on Monday, leaving more than 70,000 passengers facing travel chaos.
Government ministers and opposition parties have called on management and unions to hold crunch talks after 95% of services nationwide were axed on Sunday. The strike by members of the National Bus and Rail Union (NBRU) centres on a row over a five million euro cost-cutting plan.
Further disruption was caused when workers with other unions refused to pass picket lines, the company added.
Transport Minister Leo Varadkar said the disruption to passengers is deeply regrettable.
He said: "The unions should immediately engage with the company in talks to bring this matter to resolution. My understanding is that the company is available to engage with the unions, and has been available for many days. We must all work together to save Bus Eireann services and jobs. There is no time to lose."
NRBU general secretary Michael Faherty said drivers will not go back to work until the company withdraws it plan or sits down to renegotiate new proposals.
He added: "We made a decision, we took it because of what happened, and you can't say after a day or two that we were wrong. The guys who are on pickets are getting 100 per cent support and they will be doing the same on Monday. They don't enjoy this because next week there will be no payment, but they feel it's something they have to do."
Siptu and the Transport Salaried Staffs' Association (TSSA) have also balloted members for industrial action and will know the results on Thursday.
Bus Eireann usually carries 70,000 people on weekdays on 300 commuter, city, inter-city, and provincial services. A spokesman said the firm hopes to operate services on Monday, but that it depends on whether the industrial action continues. "If it does, then it is highly likely that we will be in the same position and will not be able to operate the vast majority of our services," he added.
The majority of the 114,000 children that use its school transport service should be carried as normal, except for 2,500 youngsters who use normal buses. Dublin Bus has not been affected.