The Mahon Tribunal has stated that a journalist could face imprisonment for publishing confidential witness statements.
The Tribunal had summoned Barry O'Kelly of the Sunday Business Post after he published details last October of a west Dublin land deal and political donations that had not been revealed by the inquiry.
Chairman Alan Mahon said the Tribunal simply could not function if media leaks were allowed to continue to interfere with witness confidentiality.
And he said Mr O'Kelly could not claim journalistic privilege because the working of the Tribunal was the overriding public interest, and that the leaks also affected the rights of witnesses concerned.
But Mr O'Kelly then took the stand, saying he was still not willing to reveal his source.
Anthony Dinan, Chief Executive of Thomas Crosbie Holdings, the Cork company which owns the Sunday Business Post, refused to give an undertaking not to publish any more leaks.
Chairman Mahon said the Tribunal would consider its position.
