Labour MEP Proinsias De Rossa has petitioned the European Union to have construction of the south-eastern motorway at the controversial at Carrickmines Castle site halted.
Mr De Rossa told ireland.comtoday he was taking the action because he felt a proper archaeological assessment of the site had not taken place.
He contended environmental impact studies on the site have been breached and since the EU was in part funding the project it should investigate the matter.
After a visit to the site this morning, Mr De Rossa said he was astonished at the extent of the area yet to be excavated.
The medieval site, which has been compared in importance to Wood Quay, has been excavated by team of archaeologists for two years, and some 40,000 significant artefacts have been found.
Earlier in the week, the Minister for Transport, Mr Seamus Brennan, announced plans that would see the proposed Glenamuck roundabout raised and tilted so the core features of the site can be preserved in situ.
But archaeologists and environmentalists have reacted angrily to the plans which would see over 40 per cent of the site lost.
It is understood an environmental group is considering taking legal action in the High Court to have construction halted.
