Raphoe publican Frank McBrearty snr has walked out of the Morris tribunal, vowing never to return.
Mr McBrearty (60) told the tribunal chairman he would not answer any more questions.
Before leaving the tribunal, Mr McBrearty read a statement in which he said that a former garda, John O'Dowd, had "used criminals and thugs to help them make false statements".
Tribunal chairman Mr Justice Frederick Morris had overruled protests by legal representatives for the Garda Representative Association (GRA), the Association of Garda Sergeants and Inspectors (AGSI) and the Garda Commissioner,in allowing Mr McBrearty to read a statement.
Objecting before Mr McBrearty read his statement, Tom Murphy, representing the GRA and Mr O'Dowd, said many of the allegations the statement contained were unproven and without substantiation.
Counsel for AGSI Seán Quinn said the statement was an attempt to publicise Mr McBrearty's viewpoint. Michael Durack, representing the Garda Commissioner, also objected, saying Mr McBrearty should not be allowed to use the tribunal to abuse people from the witness box.
Mr Justice Morris said Mr McBrearty did not have legal training and it was appropriate that the written word should be open to him.
When he finished his statement, Mr McBrearty told the chairman he would not take any more questions.
Taking the Bible in his hand, Mr McBrearty said: "My evidence in this tribunal is now complete. I will not take any more questions from anyone."
The tribunal chairman said that consequences could follow from a failure to answer questions, but the publican was undeterred, and left after a short exchange with the chairman.
Earlier, a secret tape recording of a meeting between two senior gardaí and Mr McBrearty snr, which was enhanced when used on an RTÉ Prime Time programme, was played to the tribunal.
Tribunal barrister Mr Anthony Barr SC told the inquiry the legal team had two copies of a tape recording that Insp John McGinley made of a meeting with Mr McBrearty snr in November 1996, a copy supplied by Garda Headquarters and an enhanced copy supplied by RTÉ.
On the tape, Mr McBrearty tells gardaí he had not been following them, and that the only people he asked about what gardaí were doing were his own staff members.