Ireland wants the UK to remain a full, integral member of the European Union, according to a keynote speech by Minister for Foreign Affairs Charlie Flanagan in London.
In remarks signalling a sharp departure from the UK position on immigration in particular and the debate on the EU in general, Mr Flanagan said there could be no limitations on the free movement of EU citizens as part of any renegotiation of Britain's relationship with the EU.
Mr Flanagan said: "The UK's continued membership of the EU is hugely important to us and there is too much at stake to remain on the sidelines."
He said that despite the flaws and failures, any critical review of the EU by Ireland would take as its starting point the fundamental value and importance of the EU.
In a speech to the European Council on Foreign Relations in London, the minister warned that the UK would find little support in other capitals for any limitations on the free movement of people, which he described as a fundamental right.
He said: "To try to place any general limitations on the free movement of EU citizens within the union would be to strike at a basic principle on which the union is founded.
"Equally, I cannot conceive of any way in which such limitations would find the necessary political support around the table."
Mr Flanagan conceded that the free movement principle, currently at the heart of a bitter debate in the UK about Britain's future in Europe, could be abused.
But he said a ruling by the European Court of Justice earlier this week, which found that EU migrants had to show they were looking for work and had the means to support themselves before being entitled to certain non-contributory benefits, showed that such abuses could be legitimately prevented.
Ireland had beneftted both from the right of Irish citizens to work in other EU member states, and from the presence in Ireland of other EU citizens whom, he said, had contributed in so many ways to our economy and our society.
Mr Flanagan said that on many areas, such as trade, taxation, lowering the burden of red tape, jobs, investment and growth, Ireland and the UK shared the same goals.
Shared membership of the EU had been hugely important in terms of relations between the two countries, and in terms of furthering the cause of peace in Northern Ireland.
Economically, the EU's single market helps to create British and Irish jobs, boosts British and Irish exports and ultimately fuels British and Irish growth, he said.
It is not surprising therefore, according to the Confederation of British Industry, that nearly 80% of British firms want to stay in the EU. The same would be true in Ireland where there is overwhelming business support for EU membership.
The UK exports more to Ireland than it does to China, India and Brazil while the UK is Ireland's largest export market.
Together the two countries trade over €1 billion worth of goods and services every week.
Over 200,000 jobs, on both sides of the Irish Sea, are estimated to result from the respective exports to one another.
Mr Flanagan stressed that other EU members shared Britain's concerns, and had made an explicit acknowledgement of that fact at the EU summit in Brussels in June.
"We also share with you the view that the EU must do more to restore its competitiveness and boost productivity.
"This will include the completion of the single market in services and further progress in the digital single market.
"Again, the UK will find a partner and ally in furthering this agenda in its close neighbour and friend across the Irish Sea", he said.
The minister accepted that Britain's assessment of the costs and benefits of EU membership was a matter for its own citizens.
However, he added: "I urge only that the debate be open and based on the facts."