The Taoiseach will this weekend ask the incoming Commission president, Mr José Manuel Barroso, to appoint Mr Charlie McCreevy to one of the most prestigious posts in the Commission.
Government sources said that Mr Ahern will argue that Mr McCreevy's record as Minister for Finance makes him eligible for a senior economic portfolio, such as Economic and Monetary Affairs or Competition.
Mr Ahern said yesterday that he would seek "a substantial post" for Mr McCreevy, whom he described as a "highly experienced person in many ministries".
The Taoiseach angrily rejected claims that his decision to nominate Mr McCreevy as Ireland's next EU Commissioner was motivated by a desire to remove the Minister for Finance from the Government.
Speaking in Strasbourg, Mr Ahern said that there was no truth in press reports that he had pressurised Mr McCreevy to go in order to facilitate a Cabinet reshuffle.
"It's just all nonsense. It's 100 per cent incorrect. It's 100 per cent inaccurate. It's also offensive," he said.
"It's sad, and it's annoying, and I can't do very much about it. It's the silly season and people have to fill columns and usually if they can't find anything, they just have to make it up. I think all of those (stories) were just made up."
He said he had seen stories saying he had sent people to Charlie McCreevy and that high-level party delegations had gone to him. "It's just all nonsense. None of that actually happened. But if somebody sits in an office and writes all that and checks with nobody, rings nobody - nobody ever asked me - there's not much I can do about it. That's in a democracy - freedom of speech, and freedom to write nonsense and lies is a freedom."
The Taoiseach insisted that his decision on the Commission post was made entirely on the basis of the national interest and that he had heeded calls to send a political heavyweight to Brussels.
"Charlie McCreevy is my closest colleague in the Cabinet. For the last 10 years we've been working together every day. He's a good friend. I felt really sad last night that my best and closest colleague was going to leave," he said.
During a European Parliament debate on Ireland's EU presidency earlier yesterday, the Labour MEP Mr Proinsias De Rossa condemned the decision to nominate Mr McCreevy.
"He is one of the most right-wing finance ministers in Europe. He believes in incentives. He believes in incentivising the wealthy and the rich with tax breaks and handouts, and incentivising the poor by giving them a kick in the arse," he said.
Mr Ahern said he hoped Mr McCreevy, whom he described as "my best Minister, my best confidant", would secure an important portfolio in the Commission.
"He likes Europe, although people tended to think he didn't, and he really enjoyed his period on Ecofin and I think whatever role it is, he'll do a very good job," Mr Ahern said.
"For us in Ireland, you have to have a heavyweight man or woman in that position from now on if you want to be at the centre. You need a serious person at it, and that's why I'm glad Charlie has taken up the post. I'm glad for my concept of Europe, but I'm really sorry for the home scene because that makes my life more difficult, and believe me it does," he said.
Ireland's outgoing Commissioner, Mr David Byrne, welcomed the nomination, and expressed the hope that the nominee would "inject McCreevy economics" into the European political scene.