But he said that he believed that at least two IRA moles were operating in Dundalk Garda station in 1989.
In March 2000, Mr Myers wrote an article in the Irish Times Irishman’s Diary column about a Garda mole who supplied information leading to the deaths of RUC officers, chief superintendent Harry Breen and superintentent Bob Buchanan.
Mr Myers said he first became interested in the story when he read Toby Harnden’s book Border Crossing, and later spoke to two sources, a retired Garda officer and a former IRA member.
He said the Garda source referred to former sergeant Leo Colton, and the IRA source would only identify the alleged mole as “C”, though he later learned the name Owen Corrigan.
Both Mr Colton and Mr Corrigan deny they ever supplied information to the IRA.
“I had two narratives about two different people. I put them together in the belief that they were one,” Mr Myers said.
Mr Myers said that both Mr Colton and Mr Corrigan were named to him when he was interviewed by RUC officers, but he did not confirm to them that either individual had been named to him as a source.
When interviewed by Garda officers about his allegations, Mr Myers told them “it could be said there was an active IRA cell operating in Dundalk Garda station.”
“Cell suggests a coherence that might not have existed,” Mr Myers told the tribunal. He said one of his sources told him an IRA mole had “suborned” other Gardai to provide information using blackmail.
The columnist said he had no evidence to give to the tribunal about Garda collusion.
“What I have is a report people told me. I wouldn’t regard that as evidence. It’s the basis of a newspaper article, not a trial.”
He said he could not be specific about which source provided particular pieces of information in his column, as he had assumed the two sources were talking about a single individual.
“I have to remain vague, clarity would be misleading,” he said.
Mr Myers said a newspaper column was “on a different factual plane” to a news report or editorial, in response to questions by Mr Jim O’Callaghan SC, representing Mr Corrigan.
“With the benefit of hindsight yes I would change that article, I would change a great deal,” he said.
Mr Myers said he had not read the report by Canadian judge Mr Peter Cory, as the judge had not interviewed him during his inquiry, instead relying on “imperfect” notes taken during a Garda interview by people who did not have shorthand skills.
And he said information about the murder of Louth farmer Mr Tom Oliver was given to him by author Toby Harnden.
At the end of a lengthy cross-examination, Mr O’Callaghan asked “Do you believe your article of March 2000 told the truth in a fair and impartial manner?”
“No, I don’t believe it did,” Mr Myers replied.
Mr Myers will return to the tribunal next week for further cross-examination at the tribunal.