The European Commission is expected to begin legal action against the Government today over the manner in which it has proceeded to build the M3 motorway near the Hill of Tara.
The decision will provide a boost to campaigners who are trying to force Minister for the Environment John Gormley to consider re-routing the motorway.
The legal move is not expected to halt the construction of the road, but it will force the Government to defend its position at Europe's highest court, a process that could eventually lead to the imposition of fines if it loses the case.
Environment commissioner Stavros Dimas will tell his commissioner colleagues at a meeting in Brussels today that the National Monuments Act in the Republic does not offer enough protection for important archaeological sites.
He will also highlight alleged weaknesses in Irish law that split decision-making between Irish planning authorities and the Environmental Protection Agency (EPA) for industrial projects.
He cites the Government's action at the Hill of Tara as a prime example of how it fails to conform to EU law. In a draft decision, which requires the approval of commissioners before taking effect, Mr Dimas refers Ireland to the European Court of Justice (ECJ) over these shortcomings.
"The commission considers Ireland's approach to decisions involving the destruction or removal of historic structures and archaeological monuments to be in contravention of the directive," says an explanatory note on the decision seen by The Irish Times.
The relevant EU directive says there must be a proper assessment of the effects of certain public and private projects on the environment.
The commission believes a decision not to order a second environmental impact assessment when a potentially significant archaeological site was discovered at Lismullen, close to Tara, was "in contravention of the directive".
"Because the prehistoric site was only identified in 2007, its significance could not be taken into account in a 2003 assessment of the motorway project," says the commission's explanatory note.
Despite the EU executive's concerns, in June the Government ordered that the Lismullen site be excavated without a second environmental impact assessment. It said no delay was possible due to the fragile nature of the site.
But campaigners hoping the commission would intervene directly to force the Government to halt construction of the M3 may be disappointed. The draft commission decision refers only to weaknesses in Irish legislation and does not question the Government's choice of route for the M3. Neither does it seek any kind of court injunction that would force the Government to stop work on the motorway.
The Government has argued that the motorway is a vital piece of national infrastructure and choosing an alternative route for the M3 would cause delays and cost up to €200 million extra.
Campaigners have fought a vocal campaign against the motorway, which they claim will spoil the Hill of Tara for future generations.
The commission document claims that when decisions are being taken on proposed incinerators and other industrial projects, "Irish rules do not guarantee that interactions such as those between pollution-control measures and the landscape will be adequately assessed and taken into account.There are risks that outcomes required by the directive will not always be achieved," it concludes.
The commission decision to start legal action will force the Government to defend its position at the ECJ in Luxembourg.
If it loses the legal case and does not amend its laws to conform with the relevant EU directive, it could eventually face heavy fines.
Ireland currently faces 37 infringement proceedings for breaching environmental directives.