Fianna Fail leader Micheal Martin is accusing Taoiseach Leo Varadkar of setting "a dangerous precedent" with his outspoken criticism of garda handling of the Jobstown protest.
Mr Varadkar said both gardai and the Garda Commissioner Noirin O'Sullivan should now "look into" the evidence given by officers at the marathon trial.
The Taoiseach also raised the unsuccessful prosecution of former Anglo Irish Bank boss Sean FitzPatrick.
However, Mr Martin said the comments were "very serious" and had potential implications for the gardai involved in the trial.
"I think [the comments] were ill-judged," he said.
"The courts process is, first of all, independent. The Director of Public Prosecutions (DPP) is independent. I think politicians need to be extremely careful when wandering into that domain."
Mr Martin said he was concerned about the Taoiseach's comments.
"I think they were not fair to the gardai who gave evidence during that trial," he said.
"He has left an impression, although he heavily caveats what he says to be fair, he nonetheless leaves the impression that maybe those gardai didn't give the full truth in accordance with the facts.
"That is unfair and, in my view, the jury made a decision. We shouldn't second-guess the jury."
The Fianna Fail leader said he accepted the court's decision in the case, adding that the judge was in charge and the Taoiseach should not have interfered.
"There could be other cases coming down (the tracks) in relation to that incident," he said.
"He may have prejudiced such cases. I think it is a very dangerous precedent to set. He has authority as Taoiseach and he was unfair to the gardai.
"Those gardai have their civil liberties too; they have their rights. There are all kinds of things being said on social media about them and I don't think it is on for somebody with the authority of the Taoiseach to add fuel to that and pander to those who suggested that this was some State conspiracy.
"If it was a State conspiracy, the logical conclusion is that they would have been found guilty...(but) they were found not guilty.
"In many ways this was a vindication of our courts process."
Mr Martin said the protest was not a peaceful protest and the Taoiseach was not in a position to comment authoritatively of the trial.
"If others want to make complaints there is GSOC - the judge could have made comments," he added. I don't think anyone suggested perjury was committed."