The Welsh economic development minister, Andrew Davies, has confirmed he has asked the UK government to look at keeping Wylfa nuclear plant open for up to five years beyond its scheduled closure date in 2010.
Local authorities in the Republic say they are "concerned" about reports that the Welsh Assembly government wants to extend the life of the Wylfa plant on the island ofAnglesey.
The plant is 60 miles from the east coast of Ireland and the councillors say that extending the life of the ageing plant will add significantly to the nuclear safety risks facing the Republic.
According to the All-Ireland Nuclear-Free Local Authorities Forum, the Magnox power station at Wylfa opened in 1971 but was shut down for 15 months from April 2000 when it became necessary to undertake repair work to strengthen defective welding.
The chairman of the forum, Louth county councillor Michael O'Dowd, said that "graphite in the core of Magnox reactors is known to decay over time as a result of the intense radiation it is exposed to".
He said environmentalists are concerned that an extension to the life of the Wylfa plant might result in failure of the reactor core and damage to the reactor control system, with potentially catastrophic results.
Cllr Tony McDermott of South Dublin County Council said: "Extending the operating life of Wylfa, situated just over the sea on Dublin's doorstep, would pose unnecessary risks to people in both Wales and Ireland. Extending operations beyond the designperiod would be a dangerous thing to do."
Cllr O'Dowd said the lifespan of this nuclear facility had already been extended on two previous occasions and it was a vital national issue that it should not be extended again. He called on the Government to contact the Welsh authorities and the British government on the issue.