Fianna Fáil leader Micheál Martin has said that comments by the Taoiseach on the Jobstown trial set what he described as a dangerous precedent.
Yesterday, Taoiseach Leo Varadkar said Garda Commissioner Nóirín O'Sullivan and her senior management should "look into" the evidence given by members of the force in the trial.
Last week, six men on trial for the false imprisonment of former tánaiste Joan Burton and her adviser were found not guilty by a jury at the Circuit Criminal Court.
Since then there have been calls from the defendants and their supporters for a public inquiry.
In an interview with RTÉ's Prime Time, Mr Varadkar said he did not think a public inquiry was required, but said there should be consideration given to why the prosecution was unsuccessful in this case and the trial of Séan FitzPatrick.
Speaking in Cork this morning, Mr Martin said the comments give the impression that maybe gardaí didn't give the full truth in accordance with the facts in the case.
He claimed this was unfair to the gardaí involved and Mr Varadkar's comments were ill-judged.
Mr Martin said he did not believe it was "on" for someone with the authority of the Taoiseach to add fuel to what was being said about those gardaí on social media, and to pander to those who have suggested that this was some sort of a State conspiracy.
He said both the courts process and the Director of Public Prosecutions were independent, and politicians needed to be extremely careful in "wandering into" that domain.
He also said that while Mr Varadkar adds caveats to what he says, he nevertheless gave the impression that maybe those gardaí who gave evidence didn't give the full truth in accordance with the facts.
The Fianna Fáil leader said Mr Varadkar may have prejudiced other cases coming before the courts in relation to the incident in Jobstown and that was a very dangerous precedent to set.
He added that the not guilty verdicts were a vindication of the courts process.
The Garda Representative Association has acknowledged that questions have been raised in relation to the credibility of An Garda Síochána following the Jobstown trial.
Speaking on RTÉ's Morning Ireland, GRA spokesperson John O'Keeffe said a public inquiry was not the way forward, but said he would encourage all members to assist an internal inquiry.
He said: "I'm not on here today to suggest there are no problems with the gardaí, and I'm not on here today to suggest that gardaí don't lie in court. They may have done, just the same way as anybody else.
"But what I am saying to you and what I say to the Taoiseach, whose points are reasonable - if that is the case there are correct avenues for people to follow."
He said people can seek to address issues by contacting their local garda station or by contacting the Garda Síochána Ombudsman Commission.
Gardaí last night issued a statement saying they had begun a review last Friday into the policing response and subsequent investigation of what had happened at Jobstown in November 2014.
The review is being led by Assistant Commissioner Barry O'Brien.
It will look at key learning points, organisational practices and policies which require improvement, training and other issues of note
While Solidarity-People Before Profit TD Paul Murphy welcomed the Taoiseach's comments as significant, he also said he was opposed to gardaí investigating gardaí and reiterated his call for an independent public inquiry.