All Luas staff are to be served with protective notice with immediate effect by Transdev, the operator of the Dublin light rail service.
The company said in a letter to employees that if strikes continued beyond April 24th, it would reserve the right to recover the costs of the dispute from staff engaging in industrial action.
It said the employment of staff in all four grades at the company would be on a day-to-day basis until further notice.
Earlier Tuesday, an Industrial relations and human resources expert predicted the complete shut down of the Luas service and said a Task Force could help end the ongoing industrial action.
Professor Bill Roche of University College Dublin told RTÉ's Morning Ireland there were "several possibilities" to resolve the dispute.
"A Task Force could be established as happened during a Dublin Bus dispute years ago. The Labour Court could become involved again. ICTU, IBEC and Dublin Chamber of Commerce could also participate.
“For the moment the WRC has done its job,” he said.
Prof Roche added there was “a real prospect of a full close down” which he said would have the benefit of “focusing minds where to take the dispute”.
He was commenting after Transdev informed workers it would not accept the “part performance” of employment contracts.
The company is also now expected to offer staff lower pay rises than those set out in proposals drawn up last month at the Workplace Relations Commission (WRC)and which were overwhelmingly rejected by workers.
Siptu transport sector organiser John Murphy said Luas workers are facing a lock out by Transdev.
“Basically it is a lock out without the word,” he said on Newstalk Breakfast.
“The company are saying they will let people go. There are no winners in this situation, but the company is putting its hands into the pockets of staff because they don’t like the dispute. It is a step too far.”
Siptu divisional organiser Owen Reidy said staff had attended a meeting with company management on Monday with a view to seeing if a new process to resolve the lengthy dispute could be found.
He said the management move in essence represented a threat that staff could ultimately face being locked out. He said this was unacceptable and workers would now look at an early ballot for an all-out strike at the light rail system.
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.
Informed sources said that, at the meeting on Monday, staff representatives indicated they wanted the company to move beyond the increases proposed at the Workplace Relations Commission.
These would have seen some Luas drivers receive increases of up to 18 per cent over a three-year period, including a long service increment of about 7 per cent.
It is understood management indicated the Workplace Relations Commission offer was now off the table.
Instead, it is expected to offer a deal which would not include additional long service increments.
In a statement, Transdev said it had met with Siptu with a view to exploring the basis for the union rejection of the WRC proposals, to share the financial challenges the company is facing and to outline to Siptu a revised pay proposal.
“This revised proposal takes account of the five days of industrial action since the WRC proposal was rejected and reflects the reduced financial resources available to the company.”
“Based on the meeting this afternoon it is apparent that there is no basis for any talks or other intervention in this dispute at this point. The Union’s expectations remain in excess of what was proposed at the WRC ( which in any event is withdrawn) and on that basis any discussions would have no prospect of success. In view of the additional 7.5 days of notified industrial action, the company took the opportunity to outline the serious consequences of this dispute continuing and undertook to write to Siptu and our employees setting out its position.”