The Taoiseach, Mr Ahern, said today he was "delighted" at Mr McCreevy's appointment as EU Internal Market Commissioner.
He said the EU was committed to changing the internal market and he was confident Mr McCreevy would succeed in this task. "The importance of creating a real internal market, across all sectors, in both goods and services, is vital to both business and job creation in Europe," particularly after enlargement, Mr Ahern said.
"Charlie brings an extensive range of ministerial experience and personal ability to this job," the Taoiseach added. "He has a real understanding of the European economy and has both the political experience and the technical expertise to make a success of the internal market."
The Labour Party's deputy leader, Ms Liz McManus, also congratulated Mr McCreevy on his appointment to a "significant and prestigious post that involves responsibility for an important area of EU work."
She said that while her party was "consistently critical" of many his policies as Minister for Finance, "nobody ever doubted" his abilities. Ms McManus added that she hoped Mr McCreevy will now implement policies promoting "the interests of the consumers and workers of Europe, rather than simply big business."
Mr Dan Boyle added the Green Party's best wishes, but also sounded a cautionary note. "Given his ideological bent as Minister for Finance, we hope that a less equal Europe, especially in relation to the accession countries, won't be the result of Charlie McCreevy's term in European office."
The Fine Gael enterprise, trade and employment spokesman, Mr Phil Hogan, said Mr McCreevy would now have responsibility for important areas of consumer interest such as the removal of barriers to inter-EU trade, monitoring the application of EU law across the member states and informing the public about their rights in respect to the Single Market.
"While much of this agenda has been developed over the last ten years there is a job of work still to be done, especially given the inclusion of ten new member states to the Union this year," he said.
Fine Gael MEP Mr Simon Coveney said Mr McCreevy was a good choice, as he had wide experience and understanding of the economic status and structure of the internal market.
He said he looked forward to working with Mr McCreevy to remove potential obstacles to the functioning of the internal market. "I welcome this appointment and I hope that Mr McCreevy will work to promote further competition with the EU, improve services, remove barriers to business and protect the consumer, both in Europe and Ireland."
The President of the Institute of Chartered Accountants in Ireland, Mr Terence O'Rourke, said Mr McCreevy has "rightly identified" the challenge of improving Europe's competitiveness and employment position as being his top priority.