WORK on the controversial section of the M3 near the Hill of Tara must now stop.
And the Government now faces the prospect of being hit with millions of euro in fines if it allows construction to proceed.
The Irish Independent has learned that the EU Commission has told the Goverment that no work can be carried out near the national monument discovered at Lismullin, Co Meath.
And it has ordered that a comprehensive assessment of what impact the road will have on the Tara Skryne Valley be carried out before the road is built.
The warning came as a legal challenge was launched yesterday aimed at stopping the proposed motorway.
Michael Canney from the Campaign to Save Tara group issued legal proceedings against the Minister for the Environment, the Minister for Transport, the National Roads Authority and Eurolink Ltd, the consortium awarded the construction and tolling contract.
The case centres on how the route of the motorway was chosen and Mr Canney alleges that a comprehensive assessment of each route was not carried out in line with EU law before the 'preferred' route was chosen.
And the Irish Independent can reveal that the EU Commission has warned the Government that Ireland is in breach of EU law by not carrying out a second investigation after the discovery of a national monument along the route.
Former Environment Minister Dick Roche, in one of his last acts in office, issued a direction that the Lismullin monument be excavated before the road is built over it.
But a spokesperson for EU Environment Commissioner Stavros Dimas said yesterday that Ireland was in breach of EU law by not carrying out a second Environmental Impact Assessment after the monument was discovered.
"At the moment we are still talking to the Irish authorities," the spokesperson said. "We want a second assessment. The road cannot be built until the second assessment is done.
"We have a legal disagreement with Ireland. We are saying you have now uncovered this national monument, and you cannot proceed until there is a second assessment."
In a separate development Michael Canney is seeking a court ruling that construction works on the motorway should be halted pending the outcome of the case currently being taken by the EU Commission.
The case is the first of three threatened legal challenges to the €800m motorway planned to help ease congestion on the Dublin to Meath route.
Yesterday Mr Canney said it was being taken as a 'last resort' and because the 'political and commercial backers' of the project had ignored public concerns about the road.
"It has never been my ambition to put my name forward in a legal challenge, especially a challenge against such a seemingly impregnable array of powerful political and economic forces," he said.
"I have only done so as a last resort, and only because it is absolutely essential that the silent majority who oppose this road have their concerns heard."