Former IBRC chairman Alan Dukes insisted none of the bank's customers received preferential treatment based on who they were, or the size of their loans.
is comments came as two senior ministers intervened in the dispute over Dáil privilege that followed comments made by Independent TD Catherine Murphy in the chamber about the banking affairs of businessman Denis O'Brien.
Mr Dukes said customers were treated on a case-by-case basis - but the State-owned bank's ultimate goal was to make a "maximum return" for the taxpayer. "There wasn't a general rule. No-one secured more favourable terms than others just because who they were or the size of their loan. Everything depends on the circumstance of each individual case," he told RTÉ Radio One.
Mr Dukes said Ms Murphy's information was wrong and questioned whether she would accept the outcome of a review of IBRC transactions established by the Government. "No matter what anybody on the lending side says, she continues to raise questions," he said.
The review was initiated after Ms Murphy raised concerns over the sale of Siteserv to a company owned by Mr O'Brien.
Asked if he believed there was a public interest justification in Ms Murphy highlighting Mr O'Brien's banking terms, Mr Dukes said: "I don't know what the definition of public interest is." Mr Dukes was a public interest director at Anglo Irish Bank before it became IBRC.
Ms Murphy said she checked with her source and she was standing over the comments she made in the Dáil.
Meanwhile, Health Minister Leo Varadkar intervened in the debate by insisting politicians should be free from the threat of legal action when speaking in the chamber.
However, Mr Varadkar also warned that politicians should be "careful" not to abuse the privilege by revealing personal information that might be false.
"I would agree that Dáil privilege is unrestricted and should be. The Constitution is clear on that but politicians need to be careful not to abuse it, particularly when it comes to personal information or allegations that might be false," Mr Varadkar told the Irish Independent.
Tánaiste Joan Burton also broke her silence and insisted Dáil privilege, and the media's right to report on it, is a "cornerstone of our democracy".
"The Tánaiste believes that constitutional protection for TDs and senators to speak freely in the Dáil and Seanad on matters of concern - and for the media to report it - is an absolute cornerstone of our democracy," her spokesperson said. The minister and Tánaiste's comments come as RTÉ lodges paperwork with the High Court seeking to clarify if it can broadcast a Dáil speech made by Independent TD Catherine Murphy.
The speech was made last week on businessman Denis O'Brien's banking arrangements with Irish Bank Resolution Corporation (IBRC).
Fianna Fáil called on the Houses of the Oireachtas to join the High Court case taken by RTÉ and a number of print media companies.
Fianna Fáil Senator Thomas Byrne described the restriction on RTÉ preventing the station from airing Ms Murphy's comments as a "gross violation of the independence of Dáil Éireann and the right of its elected members to speak on matters of public importance".
Fianna Fáil's Billy Kelleher said Taoiseach Enda Kenny's silence on the issue is "very serious and is compounding the constitutional crisis we're facing".
Former Attorney General Michael McDowell also weighed into the debate, saying he believes comments made by politicians under Dáil privilege should "trump" the private interests of Mr O'Brien.
Mr McDowell said he believed the court order stopping RTÉ from broadcasting details of Mr O'Brien's bank arrangements did not cover Ms Murphy's Dáil speech. He said the courts should rule that it would be "absurd and futile for some media in Ireland not to report it" as the details were in the public domain.