Work on the M50 at Carrickmines Castle is unlikely to be delayed, despite a draft EU report which is highly critical of the archaeological assessment at the site.
The report found that the initial assessment of the site had significant shortcomings on some "points of vital importance".
It identifies what it describes as a number of errors during the environmental impact assessment, describing the study as "flawed".
It also questions why no compromise solution was found after the extent of the archaeological remains became apparent in 2000.
"The important question is why the new large roundabout on the castle site became (for engineers) such an immovable component as the archaeological consequences began to become apparent, and a redesign was only entertained at the latest stage."
Aspects of the report have been rejected by the Government in a 15-page rebuttal, which claimed the review "contains serious mistakes and deals with issues outside the scope of the assignment".
Ms Margot Wallstrom, the EU Environment Commissioner, is considering the report and the Government's response before deciding what, if any, action to take.
However sources at the European Commission, which commissioned the report, believe Ireland will not face any withholding of grant aid because of its adverse findings.
Senior EU figures also said it was unlikely the commissioner would instigate legal action to prevent construction going ahead.
Work at the site has been suspended since January when protesters obtained a High Court injunction after it emerged the project had not been cleared by the Minister for the Environment as required. Last Monday Dún Laoghaire-Rathdown Council succeeded in having the injunction lifted after Mr Cullen gave his approval for the work.