The company says this is outside planned industrial action
There are fears the dispute by Luas drivers is worsening.
The company which operates the service, Transdev, is accusing drivers of taking unprecedented levels of toilet breaks - which it says is causing disruption.
The company also says this is outside the industrial action, for which notice was served.
In a letter to the trade union SIPTU, the company said that between last Wednesday, Saturday and Sunday tram drivers sought 60 "personal needs breaks".
It said these breaks caused serious disruption to the travelling public.
Two 48-hour stoppages have taken place and further strikes are planned for March 8th and St Patrick's Day - March 17th.
Martin Wall is industry correspondent with the Irish Times.
He told the Pat Kenny Show here on Newstalk the company is considering legal options and disciplinary action for workers.