The company that operates the Luas is being called on to explain a series of stoppages and delays over the last two days.
Yesterday a large section of the green line was shut down because of a power outage. There were no services at all yesterday between Balally and Brides Glen after a problem emerged near Stillorgan on Friday.
Replacement bus services were laid on, with Dublin Bus accepting Luas tickets on connecting routes.
Crews have since fixed the issue.
Meanwhile, a signal fault saw trams suspended on the red line two days ago.
Services are now back operating as normal.
However, Fine Gael Senator Neale Richmond said problems were happening too often.
"Over two days, we've had three major disruptions to the green and red Luas lines, which has caused chaos, to be honest, at this really busy time of the year," he said.
"There was a massive delay on the green line two days in a row - the line that serves Leopardstown, with its busy Christmas meet, and also people coming into town to the sales and others just on their daily commute."