Gardai are investigating an incident involving Luas ticket inspectors and a passenger at the Bluebell stop.
A video taken by a passenger on a Luas that had stopped shows a young man trying to retrieve documentation from one of the Luas employees.
The scuffle moves on to the tracks and the man is grabbed by the neck and brought forcefully to the ground by the Luas worker.
He and his colleague then drag the man on to the platform and restrain him.
The video has been widely circulated on social media, clocking up almost 120,000 views on Facebook.
Gardai attended the scene at around 5.30pm on Friday but declined to provide further comment.
"This matter is currently under investigation," they said.
A spokesperson for Transdev, the company that runs Luas, said the incident was under investigation and that "appropriate action" would be taken when the inquiry was completed.
Solidarity-People Before Profit TD Brid Smith said: "I was utterly shocked by what I saw in the footage.
"Even without knowing exactly what led up to it, there seemed to be no excusing the behaviour of the two men in uniform.
"This needs an answer from Luas as soon as possible. I'm going to write to Transport Minister Shane Ross this evening.
"I think the minister should get on to Luas immediately as this happened on Friday evening and there's still no explanation. People are looking at this saying, 'What the hell?'
"It doesn't inspire confidence and everyone I've met is saying, 'What's going on?'
"If there's an explanation other than what we see in the footage we need to hear it. Transdev need to make a public statement and explain what happened and what action is to be taken as a result."
Ballyfermot and Drimnagh Sinn Fein councillor Daithi Doolan said: "We don't know the context but from what we saw in the video it seems very heavy-handed.
"I fully appreciate the staff have challenges but I hope they are trained to use restraint.
"What I saw was deeply concerning. I hope Luas staff are trained to the best levels possible to provide support and protection to the public.
"We have to make sure these people are serving the public well."