Transdev, which operates Dublin's Luas system, has accused Siptu of seeking a "chequebook" solution to the dispute at the light rail system.
All Luas staff were served on Tuesday with protective notice with immediate effect by Transdev.
In response, Siptu - which represents workers at the company - said it was now looking at a ballot for an all-out strike which would bring the light rail service to a halt indefinitely.
A further eight strikes are scheduled to take place by staff at the company before the end of May as part of a current campaign by workers for improved terms and conditions.
Siptu organiser Owen Reidy has claimed Transdev would not have issued Luas staff with protective notice without getting "the nod" from stakeholders, including acting Minister for Transport Paschal Donohue.
Transdev managing director Gerry Madden said on Wednesday that Siptu were offering nothing by way of a solution.
“They just want someone to take out the cheque book - they don’t care who,” Mr Madden said on Newstalk’s Pat Kenny Show. “They’ve done their worst at the Easter commemorations - I hope they will reflect now, smell the coffee.
He denied Transdev was threatening the staff. “The dispute is very disruptive, they have to know there are always consequences to actions,” he said.
Mr Madden said that Transdev operates in over 20 countries and they did research but could not find a tram driver anywhere else getting close to the pay and conditions in Dublin.
“The Luas is a success story, it’s been here 12 years, in that time only two per cent of staff have left.”
Pay rates only became a problem when staff said they wanted a 53% pay rise, he said.
“I would urge Owen Reidy and Siptu to take stock, to put the play claims in line with industry norms.
Earlier, Mr Reidy said he was surprised by the “deafening silence” of the stakeholders, including Mr Donohoe.
"The Minister criticised our members at Easter over what was a legal dispute, but there is no criticism now about an employer with a state contract, getting taxpayers' money, that is effectively locking out workers and has shut off talks," he said on RTE's Morning Ireland.
Mr Reidy said that Siptu will consider a ballot on an all-out dispute, but “we will not fall into the trap of a knee jerk reaction - we will consider this carefully.”
The company said in a letter to employees on Tuesday that if strikes continued beyond April 24th, it would reserve the right to seek to recover the costs of the dispute from staff engaging in industrial action after that point.
It also warned of pay deductions for staff who were not fully carrying out their contractual duties.
It said the employment of staff in all four grades at the company would be employed on a day-to-day basis until further notice.
Strike action is currently planned for the following dates: Saturday, April 23rd; Sunday, April 24th; Thursday, April 28th; Wednesday, May 4th; Friday, May 13th; Friday, May 20th; Thursday, May 26th (Four hour work stoppage from 3pm-7pm); and Friday, May 27th.