Embattled Luas security staff have been informed that a pay deal they voted to reject is considered binding by the company and will be included in their wages.
STT Security, a private firm contracted to police the tram service, has written to staff members to inform them that an agreement previously signed by Siptu meant that the Labour Court recommendation was binding.
They have also warned they would hold Siptu and staff members liable for losses suffered as a result of any strike action.
The company has informed the union that the ballot that saw the deal rejected was considered a breach of their agreement - as would any ballot on strike action.
The company had said that anyone who does not want the pay increase of 40c per hour on their €10.75 basic rate (followed by a further 15c increase by 2017) must confirm their position in writing by tomorrow.
The recommendation was made by the Labour Court as an "interim measure" on the understanding that a reclassification of the work carried out by security staff on the Luas would be looked at.
Security guards feel that the work they do differs from other security staff, due to the high volume of people, and must deal with more incidents of anti-social behaviour.
The company had committed to doing this and, in correspondence seen by the Herald, STT had said it would also be "seeking to expand the role and responsibilities of security staff".
The Herald understands that, despite the agreement, workers in the company were keen to ballot for strike action as soon as possible and have requested that Siptu finds a way to accommodate this within two weeks.
A source has said that workers were not aware that the decision of the Labour Court was binding and now want the union to exit the deal by whatever means necessary.
Siptu did not respond when asked to comment, but has requested further meetings with the company for talks.
Separately, Luas drivers are to ballot on Monday's Labour Court recommendation aimed at resolving the four-month pay dispute with Transdev.
The service has been shut down for 12 separate days by industrial action.
The two four-hour stoppages due tomorrow and Friday have been called off for the ballot.
The decision to ballot was taken at Liberty Hall yesterday.
The new proposals include pay rises of up to 18pc.
There was no indication of whether the union would recommend acceptance, rejection, or issue no recommendation at all of the proposal.
If the workers reject the recommendation, four further stoppages are scheduled to go ahead next week.