Former Labour Party deputy leader Brendan Howlin has confirmed that the McBrearty family's lawyer was the source of his information that led to the creation of the Morris tribunal into Garda corruption.
Mr Howlin said that Martin Giblin, a senior counsel, whom he spoke to yesterday, has now released him from any obligation to continue protecting his identity.
The tribunal had previously tried to find out the source of Mr Howlin's information, resulting in a Supreme Court judgment last month that he must hand over his phone records.
However, Mr Howlin says that Mr Giblin revealed his identity to the Morris tribunal in October 2003 and that this information was also given to the gardaí.
Brendan Howlin
Speaking on RTÉ radio, Mr Howlin said it was not clear why the tribunal pursued him through the courts for information that it already possessed.
"If there was a compelling reason that this information was discernible by no other source, there was some coherent case but, as the information had already been given to them, why this happened is a mystery to me," he said.
The Wexford TD added that the tribunal had attempted to undo the principle of confidentiality of information given to public representatives.
"The decisions that have been made now weaken the role of the Oireachtas itself in holding important agents of the State, like an Garda Síochána to whom we give extraordinary powers, accountable," he said. "That can only happen if citizens can reach out to TDs that they trust without fear."
Labour Party leader Pat Rabbitte said the Supreme Court judgment, which overturned an earlier High Court ruling that Mr Howlin was entitled to protect Mr Giblin's identity, had profound implications for all TDs.
"The principle of allowing unfettered access and communication between citizens and elected representatives remains one for the Dáil to address," he said.
"For any institution to seek to undermine this principle would require clear and overwhelming reasons. There does not appear to have been any such justification in this case."
A spokesman for the Department of Justice, which has responsibility for tribunals, said yesterday that the tribunals were independent in their functioning and that the Department had no comment.