Bus Éireann has informed staff of a programme of significant cuts to premium payments, allowances and reductions in temporary staff in a bid to avert insolvency.
The company says that if the reform programme is fully implemented, it is prepared to offer staff a pay increase averaging 2% a year for four years.
The National Bus and Rail Union has said the pay rise offer of 1-3% was insulting, given that the proposed cuts would reduce pay by over 25%.
Meanwhile, SIPTU described the proposals by Bus Éireann as being "totally horrendous and totally unacceptable". The union also said that a mandate for industrial action may have to activated.
In a letter to staff, Acting Bus Éireann CEO Ray Hernan warned staff that the company will go out of business if its financial difficulties are not addressed.
The required changes include cuts in premium payments, overtime rates, rota and shift payments, and allowances.
In future sick benefits will only be calculated on basic pay.
Staff will have to accept redeployment and what he calls reasonable changes to roles and responsibilities.
Mr Hernan says the company will also seek to reduce or eliminate the number of temporary staff.
Where meaningful work is not available - or staff refuse reasonable alternative work or redeployment, they will be put on short time or layoff as appropriate.
He pledges to retain the Expressway division, to protect the maximum number of viable jobs, and to safe-guard basic pay.
He stresses that there will be no voluntary severance scheme at this time - but any redundancies that do arise will be on terms of 2.5 weeks per year of service plus statutory redundancy.
Mr Hernan urges unions to be responsible and accept the changes for the sake of the future of Bus Éireann.
He stresses that the company will have to resolve its difficulties through its own resources, with no assistance from the taxpayer, adding that an increase in revenue for services like free travel will not fix its problems.
He says the restructuring of the company will be at a pace and time that the company can afford and subject to a rigid cost benefit analysis.
He says the company must provide a premium service that is value for money for the customer and the taxpayer.
Mr Hernan stresses the urgency of rapid implementation of the proposals, and has invited the unions to talks on 24 January.
Responding to the company's position, NBRU General Secretary Dermot O'Leary said: "It is nothing short of scandalous that Bus Éireann would resort to attacking its own staff through cutting their wages to facilitate the minister and his department into becoming a reincarnation of Pontius Pilate in denying all responsibility for creating the Expressway crisis.
"Attempting to ensnare ordinary workers into a labyrinth of political deceit is disgraceful, and clearly demonstrates the contempt that those who make policy, those that implement policy have for decent workers who go about their daily toil far, far away from where life-impacting decisions are made."
He added: "We have today informed Bus Éireann Management that we will not accept any imposition of cuts to our members' pay, we also advised that there was a real danger here that the transport infrastructure in this country could be forced into industrial turmoil if such an attack was initiated.
"The responsibility for this crisis goes way beyond industrial relations parameters, the fingerprints of a number of Government agencies are all over the crime scene here; the Department of Transport, NTA, NTMA and the Department of Social Protection have all had a part to play in forcing this once proud transport company to its knees; staff for their part had the perfect alibi, they were providing a public transport service for the citizens of the State.
"We will now arrange to meet with trade union colleagues over the next number of days to agree on a coordinated and united approach to this stomach-churning initiative."
In a statement, SIPTU Sector Organiser Willie Noone said: "For a semi state company to issue ill thought out proposals after months of inertia that effectively want to introduce casualisation of work, redeployment to wherever the company want you to go, destroy the pension scheme, reduce numbers, introduce privatisation and outsourcing of work, undermine the integrity of all categories of workers especially clerical by stating they are effectively overpaid, reduce meagre shift and premium payment and expecting workers to accept everything the company wants without question now and for the future is simply unbelievable and shocking.
He added: "It is clear that this Trade Union will not be accepting these proposals as sought and as an apparent precondition to meeting on the 24th January and the facile attempt to seek the Labour Court to reconvene is deplorable as this same company would not engage with the [Labour] Court on the 6th December and none of these proposals has even been discussed with the Trade Unions at this stage.