Ireland has weighed into the heated row over Britain's future in Europe, warning that any exit from the EU would pull the two neighbouring countries apart just as they are forging historically close links.
Dublin's Foreign Affairs Minister Charlie Flanagan said the Irish are dismayed at the prospect of the UK going it alone and could not simply sit by as debate intensifies ahead of a proposed make-or-break referendum on membership in 2017.
In a direct plea to Britain, he said: "While I'm fully respectful of and sensitive to the internal democratic reflection under way within the UK, I cannot shy away from this debate.
"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."
Mr Flanagan added: "Ireland's position on this is unequivocal: we want the UK to remain a full, integral member of the Union."
Speaking in London at the European Council on Foreign Relations, the senior Irish government minister, who also has responsibility for trade, said the EU laid foundations for unparalleled peace and stability across the continent.
"That ought to be appreciated here in the UK, which sacrificed so much in two world wars precisely because of the absence of a settled European order based on law," he said.
"The role of the EU in bringing about and maintaining that peace and stability should never be underestimated or taken for granted."
Just this week, former UK prime minister Sir John Major predicted Britain would leave the EU unless genuine reforms could be achieved in the next three years.
Acknowledging genuine British concerns about power in Brussels, Mr Flanagan said Ireland shared many of them and would be a "key ally and partner" to its nearest neighbour in pushing for reforms.
The EU needs to do more to loosen red tape and over-regulation while problems with an ever-closer Union and the role of national parliaments could also be addressed, he added.
Turning to the immigration debate in the UK, Mr Flanagan said abuses of the right to free movement could be legitimately prevented.
Stressing that Ireland and the UK are "like-minded on very many issues", he said the two nations are "closer to one another than to anybody else in the EU".
The UK is the single most important champion of many European policies backed by the Irish, he told the audience of diplomats, commentators and media.
"That is one key reason why we view with dismay the prospect of a UK marginalised within the EU or, still worse, outside it altogether," he said.
"Such an outcome could also have substantial practical effects on many areas of our economy, society and public administration.
"But more than that, it would pull our two countries further apart just as we have been growing closer."
The minister pointed out that the UK exports more to Ireland than it does to China, India and Brazil while the UK is Ireland's largest export market, trading more than 1 billion euro worth of goods and services every week.
It is estimated more than 200,000 jobs, on both sides of the Irish Sea, rely on trade between the countries.
The EU has created the conditions which help this trade, he said.
Mr Flanagan said it was Ireland's duty as a close friend and neighbour to offer honest advice to Britain.
"The last thing Europe needs right now is another round of self-absorbed introspection," he said.
"It would be an unwelcome and energy-sapping distraction, when the focus should be firmly on our economies and on re-connecting with our peoples."
Mr Flanagan said the EU had transformed Ireland for the better, was hugely important in improving relations between the British and the Irish and its role as a force for peace in Northern Ireland could not be overlooked.
"The warm relationship between the UK and Ireland is one of the great advances of my political lifetime," he said.
"The close ties between our two countries can only be further reinforced by our continuing joint membership of the European Union.
"Having joined the club together over 41 years ago, it's my fervent hope that we will continue working side by side within it."