Writing in the UK's Financial Times, he said that the aims of the CAP (common agricultural policy), such as guaranteeing the availability of food supplies at reasonable prices and of ensuring a fair standard of living for the agricultural community, remain just as valid today.
"The Common Agricultural Policy has in recent months been the subject of much criticism, with repeated calls for further reform," he wrote.
"The 2003 reform was the most radical of all. This reform is in its first year of implementation, and it would be both unfair and unwise to ask farmers to accept another radical reform now."
However the CAP has come under intense criticism from some quarters. The EU currently spends around 40 per cent of its budget on agriculture, a figure that the British Government argues is too high.
Britain is the fifth largest recipient of EU agricultural aid, receiving €9bn per year of which €3.5bn is given in subsidies. France is the largest recipient, getting around €23bn in aid - €9bn more than any other member state.
Scandal recently broke out in the British press after it was revealed, under the Freedom of Information Act, that some of the UK's wealthiest people were receiving hundreds of thousands of euros in CAP funding.
Nonetheless, Ahern argues that attempts to overturn an agreement reached unanimously by the European Council in October 2002 would send out the wrong signal.
"The public needs to see a Europe that stands by its agreements," he said. In addition, he argued that to embark on another reform of CAP would handicap the EU in the upcoming WTO negotiations and remove the motive for other big food producers to move towards reform of their agricultural sectors.
He also argued that Europe is at a big competitive disadvantage when it comes to farm size. The average farm size in the EU15 member states is only 18 hectares, compared with 178 hectares in the US.
"It is clear that if the EU eliminated or significantly reduced support for agriculture, European farms on the margins of commercial viability would go out of business and European agricultural production would fall rapidly," he said.
As far as Ahern is concerned, calls for radical CAP reform are misplaced.