Eamon Dunphy told the Mahon tribunal that if Cork developer Owen O'Callaghan were to swear to the inquiry that he did not pay Taoiseach Bertie Ahern for tax designation in Athlone in 1994, he would believe him.
The broadcaster had told the tribunal that Mr O'Callaghan had said he had "taken care" of Mr Ahern, so that he would get tax designation for his development at Golden Island in Athlone.
However, he had also described Mr O'Callaghan as an "honest, first-class and thoroughly decent person".
Counsel for Mr O'Callaghan, Paul Sreenan SC, asked if he would accept what Mr O'Callaghan said if he came to the tribunal and denied he had paid Mr Ahern.
Mr Dunphy responded that he would insist that his inferences were honestly drawn.
"I believed him when he made those remarks about his relationship with Mr Ahern, but I also accept that the inference I drew was an inference," he said. "If Mr O'Callaghan was to come in here and say that I was mistaken, well yes, I'd accept that."
Counsel for Mr Ahern, Colm Ó hOisín SC, pointed out that Mr O'Callaghan had made a substantial contribution to the Fianna Fáil party in the mid 1990s. He asked Mr Dunphy if he thought it possible that Mr O'Callaghan's negative attitude to Mr Ahern was because he felt "a little let down" when he did not get support from the Taoiseach for his stadium project.
"It's possible to put that construction on it," Mr Dunphy said.
He said he had the highest regard for Mr O'Callaghan and didn't wish to damage him unfairly.
"I can't be sure if Mr O'Callaghan did or did not do anything . . . I'm telling you, as I told the tribunal, what I know was said and I can't put it any higher than that," Mr Dunphy said.
Mr Ó hOisín also said Mr Ahern was not responsible for the tax designation for Golden Island. However, counsel for the tribunal, Des O'Neill SC, interrupted to say that the designation order was signed on December 14th by Mr Ahern, the day before the change of government and "was probably the last ministerial act of Mr Ahern".
Mr Sreenan accused Mr Dunphy of attending the tribunal to "wreak revenge" for what happened to his journalist friend, Frank Connolly.
He said Mr Dunphy had "wittingly or unwittingly" been used by Mr Connolly to get revenge after the enterprise he was head of, the Centre for Public Inquiry (CPI), was closed down.
Funding for the CPI was withdrawn by US philanthropist Chuck Feeney in December 2005, after a statement in the Dáil by then minister for justice, Michael McDowell about a Garda file on Mr Connolly regarding his travels to Colombia.
Mr Dunphy said the idea that he would allow himself to be used was nonsense. He said the suggestion that he would come to the tribunal and perjure himself, and damage a Taoiseach and a businessman for whom he had great respect was "outrageous" and "a preposterous allegation".
He said he did feel that the treatment of Mr Connolly had been "dastardly", and said that afterwards, "some iron entered my soul", but he denied that it compelled him to come forward.
Mr Dunphy conceded there were inconsistencies in his statements to the tribunal, but said he had done his best to tell what he knew, "contradictions and all".