Michael McDowell has told the Dáil that it was his constitutional duty to make public the information he had concerning the executive director of the Centre for Public Inquiry, Frank Connolly.
The Justice Minister said he has acted within the law and said he did not breach the confidentiality of any citizen. He claimed he made the allegations in order to defend national security.
Mr McDowell said it would be a sad day for Ireland if any of his predecessors or successors, faced with the same situation, failed to act in the same way.
The Opposition has accused the minister of abusing his position and called for his resignation.
Fine Gael's Jim O'Keeffe criticised what he said was the release by the minister of a copy of an official garda file which could be used in a trial.
Labour's Joe Costelloe said Mr McDowell was acting as DPP, judge, jury and executioner.
Earlier, the chairman of the Centre for Public Inquiry lent his support to Mr Connolly.
In an interview on RTÉ's Morning Ireland, Mr Justice Feargus Flood said that every citizen is entitled to a presumption of innocence until proven otherwise in a court of law.
His comments follow Minister McDowell's revelation yesterday that he had given documents to the Irish Independent for their story alleging that Frank Connolly had travelled to Colombia in 2001 on a false passport.
Mr McDowell earlier alleged under privilege in the Dáil that Mr Connolly had travelled to Colombia on a false passport when he was a journalist in 2001.
Judge Flood says that he stands four square behind Frank Connolly, saying he does so with any citizen until they have gone through the due process of law.
He said all citizens are innocent until proven guilty, in accordance with the rules of law, and said he would not pass judgements on anybody until that was met.
He said the Minister for Justice cannot override the constitution, which states that justice shall be administered in courts, adding that the only person who can decide whether a citizen is to be prosecuted is the DPP, and no one else.
Judge Flood also cast some doubt over whether the organisation can continue with its work, saying the centre cannot operate without money. Last week, Atlantic Philanthropies withdrew its funding.
Mr Flood said that current funds will run out by the end of the year and the staff will have to be let go.