The Taoiseach has been accused of "flunking" a test of his socialist credentials set by Socialist Party's Mr Joe Higgins.
In the Dáil this morning, Mr Ahern was set three questions by the West Dublin TD.
Joe Higgins
Mr Higgins was cheered on as he dismissed the Taoiseach's claim that he was one of the last remaining socialists in Irish politics as "ludicrous" and warned that socialism was not a flag of convenience.
"You can imagine how perplexed I was when I found my wardrobe almost empty," he told the Dáil. "The Taoiseach had been busy robbing my clothes."
To howls of laughter, Mr Higgins said his first reaction on hearing of Mr Ahern's new-found commitment to socialism was "good".
"I thought great - the two of us will go down together," he said. "But sadly I had to take a reality check, and if this confession was genuine we would have to go back 2,000 years to find one as rapid and as radical."
His test comprised three questions on public ownership, the Iraq occupation and equality. "You have three minutes so I suggest you give a minute to each of the tests and then I'll judge at the end," he said.
But the Taoiseach said he would never consider himself the same type of politician as Mr Higgins. "For three decades I've watched him and I've never heard him say a positive things about anything," he said. "He (stands for) a utopia that doesn't exist."
As tensions rose, an ensuing row saw independent Dr Jerry Crowley dismissed from the Dáil when he lost his temper after Mr Ahern accused him of being a "right wing doctor".
Around 15 minutes later, Mr Higgins announced that the Taoiseach had failed the test. "He couldn't answer A, couldn't answer B and so spent all his time trying to answer C," he said. "On that basis alone he has flunked the test."
He asked Mr Ahern to withdraw his comments about socialism but the Taoiseach said he was trying to make the point that resources could not be distributed to education, health and welfare unless the wealth was generated.