The National Transport Authority has rejected claims that it is privatising bus services in Ireland.
NTA Chief Executive Anne Graham said privatisation would involve a transfer of ownership and loss of public control, which she said was not the case.
Unions at Dublin Bus and Bus Éireann have escalated their plans for industrial action over plans to put 10% of routes out to private tender.
SIPTU and the National Bus and Rail Union are now planning to hold two 48-hour stoppages on 1 and 2 May, as well as 15 and 16 May.
They are also planning a three-day strike on 29, 30 and 31 May.
Unions at the two State bus companies fear that if 10% of bus routes are opened up to the private sector, it could trigger a deterioration in the pay and conditions of members.
Ms Graham urged unions not to take industrial action, adding that the NTA would impose fines of €150,000 a day on Dublin Bus and €80,000 on Bus Éireann for failing to provide a service during the strikes.
However, commenting on the loss of revenue to the companies, she acknowledged that they would save some money by not paying wages.
She said that any Bus Éireann or Dublin Bus employees who had to transfer to private operators would have their terms and conditions preserved for the duration of the new contract.
However, she acknowledged there was nothing to stop the private contractors from paying new recruits nothing more than the minimum wage.
Ms Graham also confirmed that there was no obligation from EU legislation forcing their hand.
She said the NTA would vigorously defend the judicial review proceedings taken against it by the National Bus and Rail Union.
Ms Graham also defended the criteria for the tenders which some private companies have claimed would set the bar too high for Irish firms to successfully compete.
NBRU General Secretary Dermot O’Leary criticised the NTA’s comments.
He said: "The NTA are obviously attempting to extricate themselves from their responsibility as regards the decision to privatise 10% of publicly-owned bus routes.
"The fact is, taking services from a public company and giving them to a private company is one of the fundamental cornerstones associated with privatisation.
"Attempting to fudge a response to our contention that this is a race to the bottom by saying that both Dublin and Bus Éireann can compete for the contracts, whilst at the same time admitting that one of the main reasons for tendering is to actually establish a comparator to assess value, is totally contradictory."
