Kildare County Council is taking legal action in the High Court against An Bord Pleanála's decision last June to refuse planning permission for the proposed Athy inner relief road.
This is only the second time in its nearly 30-year existence that the board has faced a legal challenge from a local authority.
Kilkenny County Council initiated proceedings in 1991 over its ruling on a quarry, but later withdrew.
It is the first time any council has challenged a ruling by the appeals board on a road plan. However, the scheme for Athy was the first adverse decision by the board on any road plan since it started adjudicating on them in January 2003.
The Athy inner relief route, first proposed in 1975, would run south of the main street - Duke and Leinster streets - from a new roundabout west of the railway bridge on the Dublin road to another new roundabout on the Kilkenny road.
It was to include new bridges over the Grand Canal and the River Barrow.
Objectors argued that the route would run right past the rear of Athy's courthouse - a protected structure - skirting the main square before rising to cross the river.
In its ruling, An Bord Pleanála said it considered that the proposed 1km route "would fail both as a street and as a relief road because it would continue to bring traffic, including heavy commercial vehicles, through the town centre".
It also ruled that the environmental impact statement on the scheme had not adequately addressed alternatives - including a proposed southern bypass, which would provide a new crossing of the River Barrow just 500 metres away.
Though the inspector who conducted the public inquiry last March recommended approval, the board said "the injurious effects on the town of Athy would be unacceptable in the context of proper planning and sustainable development".
Kildare county secretary Charlie Talbot confirmed yesterday that the council had "initiated proceedings to have An Bord Pleanála's decision judicially reviewed" - an executive decision made by county manager Niall Bradley.
Athy solicitor Frank Taaffe, who was the most prominent opponent of the inner relief route, said members of the county council, who were informed only on Monday last, should call for Mr Bradley's resignation if the legal action failed.
In a statement issued on behalf of the Athy Urban Development Group, which campaigned against the relief route, Mr Taaffe said the effect of the county manager's decision would be to delay the adoption of alternative measures.
"If, as I expect, the High Court rejects the county manager's call for a judicial review, then I feel the members of Kildare County Council should call on the county manager to step down from his position," he added.
Athy Chamber of Commerce president Adrian Conlan told the Kildare Nationalist: "We would deem the matter at this stage closed."
