Irish PM Brian Cowen, pictured with Italian PM Silvio Berlusconi, wants to hold a re-run of the poll.The controversial EU constitution is set to come into force by next January after a deal was reached with Ireland in Brussels today.
EU leaders agreed to offer a number of concessions to Ireland's leaders so they can persuade voters to back the Lisbon Treaty in a new referendum later this year.
The news came as French President Nicholas Sarkozy boasted that the EU's powerful new financial regulators will exert unprecedented control over the City of London.
Mr Sarkozy accused Prime Minister Gordon Brown of caving into the Brussels power-grab over Britain's financial centre following a meeting of EU leaders.
His provocative comments are set to infuriate the Prime Minister, who earlier insisted he had fought off attempts for the European institutions to override decisions made by the British Government.
The two new bodies - the European Systemic Risk Council and European System of Financial Supervisors - which will be in charge of regulating and supervising banks across the continent.
But there have been concerns that the bodies would be able to give orders to countries - for instance, to bail out a failing bank.
Critical: Nicholas Sarkozy has accused Gordon Brown of caving into the Brussels power-grab over Britain's financial centre
The summit conclusions, agreed by the European Council, stresses "that decisions taken by the European Supervisory Authorities should not impinge in any way on the fiscal responsibilities of member states".
But they also agree that the bodies will have 'binding and proportionate decision-making powers (over) whether (national) supervisors are meeting their requirements under a single rule book and relevant (EU) law".
The Irish people threw the EU into disarray last June by rejecting the Lisbon Treaty - which critics say is the EU constitution in all but name.
Irish Prime Minister Brian Cowen wants to hold a re-run of the poll in the first week of October and there is widespread expectation that voters will back the Treaty second time round.
In a classic Brussels fudge, Mr Cowen won legal guarantees that the EU will not be able to override Irish policy on the military, tax and abortion.
But the guarantees will not be ratified by member states until long after the Treaty comes into force - meaning that Tory leader David Cameron will be in the awkward position of having to steer them onto the statute books if the Conservatives win the next election.
The Conservatives are opposed to the Lisbon Treaty and have promised to hold a referendum on the Treaty if it has not been ratified by the time they win power.
If the Irish public vote 'yes' and the final remaining countries complete the ratification process, EU leaders hope that the Lisbon Treaty will come into force by January 1, 2010.
Ireland's financial circumstances have weakened considerably since the referendum 'No' vote last year, meaning that voters will be more reluctant to upset EU allies by rejecting the Treaty for a second time.
One of the most controversial aspects of the Treaty is the creation of an unelected EU President - a post which former Prime Minister Tony Blair is in the front-running for.
The British public have been denied the chance to vote on the Treaty, which is almost identical to the EU constitution, despite a Labour pledge to hold a vote at the last general election.
Mr Brown insisted that the Irish guarantees will not affect the Treaty - which has already been ratified by the House of Commons.
He said: 'The guarantees are specific to Ireland. The summit conclusions set out the fact that the protocol does not change the relationship between the European Union and the member states, and that the protocol clarifies but does not change the content and application of the Treaty.'
The Irish protocol will become part of the next EU Treaty change when Croatia joins the Union.
This is expected in the next couple of years.
Supporters of the treaty - a complex set of institutional changes aimed at making the enlarged EU more efficient - were keen to avoid any new round of referendums on it, after years of negotiations.
