Minister for Foreign Affairs Dermot Ahern has told the British government that any move to build a nuclear power station in Northern Ireland would damage Anglo-Irish relations.
The warning came amid mounting speculation about plans for new nuclear stations in the wake of an energy review currently under way in Britain.
Mr Ahern raised the Government's opposition to the development of any new nuclear power stations during a meeting with British government representatives last week.
The energy review is widely expected to lead to a decision by the Labour government to proceed with the construction of upwards of 10 nuclear power stations.
Sites of new stations are expected to include Sellafield in Cumbria and northwest Wales. The possibility of a nuclear power plant in Northern Ireland has not been ruled out either.
During a meeting in London last week Mr Ahern told the Northern Secretary Peter Hain that the Government remained totally opposed to nuclear power.
A spokesman for the Minister said Mr Ahern had "made it crystal clear to the Secretary of State that any move to build a nuclear plant in the North would damage relations between both governments.
"He also said the Government would be strenuously opposed to any new plants, particularly in Wales and the west coast of England.
"This is an issue on which he holds very strong views, not least because he and his constituents have to live with the pollution and safety threat posed by Sellafield, just a short distance across the Irish Sea from Dundalk Bay.
"The Minister made it very clear to Mr Hain that the Irish Government would be vehemently opposed to the building of any new nuclear plants, which is under consideration as part of the UK energy review.
There is no doubt that Mr Hain and the British government understand the outright opposition to nuclear power which is a cornerstone of Irish Government policy, the spokesman added.
Last month the British government launched a consultation paper on the future of British energy policy, warning that dwindling oil reserves and geopolitical instability gave an added urgency to formulating a new policy.
Following a consultation period, it will formally announce its new policy in the early summer.
The British government is officially neutral on the issue of nuclear power, but the prime minister, Tony Blair, has indicated his support for new nuclear plants.