The Taoiseach has insisted revelations about a 27-year relationship between Mr Charles Haughey and the journalist Terry Keane are a matter for themselves.
Mr Ahern said the matter had no political implications.
Attending a party for broadcaster Gay Byrne in Dublin last night, the Taoiseach said he had not seen Friday's Late Late Show on which Ms Keane spoke about the affair.
Mr Ahern added: "They are two private individuals. It's a matter for them."
Government sources had earlier declined to comment on the affair - more details of which were published in yesterday's Sunday Times.
The sources dismissed suggestions that it had any power to damage the Government.
When telephoned at his Kinsealy home yesterday and asked by The Irish Times if he had anything to say in response to Ms Keane's revelations, Mr Haughey quickly put down the phone.
But Fianna Fail TD and European election candidate Mr Ben Briscoe criticised Ms Keane for causing "hurt that was unnecessary and beyond description" to the Haughey family.
"By writing a book, selling those rights and hyping it on the Late Late Show, she showed her clear motivation.
"The place for an apology to the family was not on television or in the public prints, but privately."
The episode illustrated "the growing trend in Irish public life to intrude into what ultimately are private matters", he added.
Socialist Party TD Mr Joe Higgins said Ms Keane's revelations amounted to a "betrayal of privacy".
He added: "I suppose this is in keeping with the morality of the so-called Golden Circle in which they moved, where in the order of priority, personal loyalty came way behind self-advancement and financial reward."
Fine Gael, in a statement, cautioned on the dangers of confusing the public interest with what was merely interesting to the public.
The statement questioned whether Ms Keane's revelations were of legitimate interest given the "disproportionate hurt that may be caused to some private individuals".
Meanwhile, referring to Ms Keane's suggestions that she played a role in influencing a judicial appointment, the party's European election candidate, Mr Jim Mitchell TD, said it would be unfair to single out any particular judicial appointment for criticism.
Mr Mitchell said: "The reality is that almost all judicial appointments and promotions since the foundation of the State have been as a result of political lobbying."
Yesterday, Ms Keane's former employers, the Sunday Independent, claimed she would receive a financial package worth almost £600,000 over two years "for her act of ultimate betrayal against the former Taoiseach".
But the editor of the Irish edition of The Sunday Times, Mr Rory Godson, said neither that figure nor another putting her new salary at £85,000 a year "bear any relation to what she's getting".
He said The Sunday Times had an extended print run of 162,000 copies to deal with expected demand yesterday, an increase of 30,000.
Ms Keane was helping the newspaper with next week's instalment but she was not available for comment last night, he added.
Speaking on Friday night's Late Late Show on RTE 1, Ms Keane said she was going public about the 27-year affair to pre-empt another book, by two Independent Newspapers journalists.
This would portray the affair as "a loveless relationship, punctuated by dinners and trips on yachts".
She said she had decided to tell her own story first.
Announcing she had left the Sunday Independent, she criticised her former gossip column in the newspaper, "The Keane Edge", saying she had become unhappy about it over the years.
She said: "Although it was under my name, I did not write all of it," she said.
Of Mr Haughey, she remarked: "I love him. I think he loved - loves - me very much."
Asked by Gay Byrne if they had ever considered "running away", she said: "No, we were both married."
She added: "Charlie was an old-fashioned man."
Her husband, Mr Justice Ronan Keane, knew she was writing the book and was "fully supportive", she said.
She said the book would also deal with subjects such as her earlier experience as a single mother.
"It's my story. It's what happened to me, not just about Charlie."