Wexford had a lower Gross Value Added (GVA) rating than Kerry in 1995, according to figures released by the Central Statistic Office yesterday.
The county-by-county breakdown is expected to fuel political debate about the Government's decision to add Clare and Kerry to a new western seaboard region in its application for 15 counties to retain Objective 1 status for EU funding.
Louth, in the Border region, has a GVA of 111 relative to the EU average largely because of the industrial presence of Coca-Cola in the county.
The figures emerged in a Dail response to a question from the Labour leader, Mr Ruairi Quinn.
A Government spokesman later said the Government's application to Eurostat to have the State divided into two regions for structural fund purposes was based on 1996 statistics for the regions, including the new region of the western seaboard.
The spokesman and the CSO itself indicated that the county breakdown, based on 1995 figures, were compiled for the purposes of the Dail reply. The figures were "best available estimates" but "not reliable enough to be regarded as official statistics".
The CSO also stresses that the GVA, a statistical concept normally used for broad regions, was an indicator of output. It was not a measure of the wealth of each county.
The workforce producing the GVA in a county might not live there and might bring their incomes home to a neighbouring county. Similarly, the GVA for individual counties might be particularly influenced by the presence of large industrial enterprises whose profits might be remitted elsewhere.
The Taoiseach, Mr Ahern, said on the basis of the figures supplied by Eurostat last week, the combined Border, west and midlands region would be 72.3 per cent of the EU average. The addition of Clare and Kerry would bring this figure to 73.3 per cent.
The Labour finance spokesman, Mr Derek McDowell, said the county breakdown figures did nothing to add to the Government's case for retaining Objective 1 status for part of the country. The manner in which the Government had presented the figures was dishonest, he said.
Instead of using 1996 figures which were available to Eurostat, they had chosen to use 1995 figures. These figures were calculated on the basis of Irish GDP per capita being 92 per cent of the European average, whereas the most recent figures from Eurostat set the Irish figure at 97 per cent of the EU average, he claimed.
