The Irish Council for Civil Liberties has said it strongly condemns the Garda operation at yesterday's "Reclaim the Streets" protest in Dublin.
The organisation says it has received reports of undisciplined Gardaí recklessly baton charging and verbally taunting peaceful protestors, many of whom were teenagers.
Liam Herrick said such action was inevitable given the almost complete impunity that members of the Gardaí had enjoyed in recent years.
Meanwhile, the Minister for Justice, John O'Donoghue, has ordered a full report into the Gardaí's handling of the anti-capitalist demonstration.
A senior Garda spokesman has told RTÉ News that everything would be done to establish what happened. Superintendent Ray McHugh said every Garda involved would be interviewed to try to establish the facts.
Superintendent McHugh said people have the right to go about their business unhindered but people also have the right to protest peacefully. He said anyone with a complaint should contact the Garda Complaints Bureau.
The Labour Party and the Green Party have said the Gardaí's handling of yesterday's protest emphasised the need for an independent assessment of the force.
Eighteen people have been charged with a range of offences after violence erupted during the rally. Witnesses have accused the Gardaí of using excessive force. Video footage shows the Gardaí using batons to move people off a city centre street.
About 400 people attended the demonstration, which the organisers say was supposed to have been a street party. The situation appeared to get out of hand when the rally reached College Green and protesters sat on the street.
Witnesses said people as young as 16 were injured by batons. They said some suffered head injuries, while others were severely shocked. There has been criticism that at least one of the Gardaí involved was not wearing his identification badge.
