A group of residents can continue with their legal challenge to an extension to the Ringsend sewage treatment plant in Dublin after a decision by the Supreme Court today.

The State and Dublin City Council had appealed against a High Court ruling allowing the Sandymount and Merrion Residents' Association to challenge An Bord Pleanála's decision to give the go ahead to the extension.

It was claimed the residents did not have the legal standing to bring the challenge.

The Supreme Court rejected the appeal by the State and Dublin City Council.

The court will give its reasons at a later date.

The residents are objecting to the €270m extension because of concerns about the environmental impact of the project.

It will include a 9km tunnel under the sea to discharge treated effluent into Dublin Bay.

The board granted permission for the project late last year, just weeks before Minister for Arts, Heritage and the Gaeltacht Jimmy Deenihan proposed to designate a 40km stretch from Howth to Dalkey Island as a special area of conservation.

The residents said the undersea pipe will discharge treated effluent into the conservation area and an Environmental Impact Statement was inadequate.