Chancellor George Osborne has insisted it is in Britain's national interest to commit billions of pounds to help bail out the Irish economy.
He said the UK is making a separate bilateral contribution to the rescue package to reflect the fact that it is not in the euro, and confirmed Britain's total exposure is "around" £7 billion.
The Irish Government confirmed last night it was seeking the bail-out funds and talks are under way to confirm details of the package negotiated with the EU and the International Monetary Fund. The UK has also offered a separate loan.
Critics of the British part in the bail-out claim UK taxpayers are being asked to save the euro, but Mr Osborne said bluntly: "'I told you so' is not much of an economic policy."
Mr Osborne said: "What we have committed to do is to be partners, as shareholders in the International Monetary Fund, in an international rescue of the Irish economy.
"But we have also made a commitment to consider a bilateral loan that reflects the fact we are not part of the euro and don't want to be part of the euro.
"Ireland is our very closest economic neighbour. I judged it to be in our national interest to be part of the international efforts to help the Irish."
Asked to confirm the £7 billion figure, Mr Osborne replied: "It's around that. It's in the billions, not the tens of billions."