"This is enough for me to recommend that Britain remain in the European Union," Cameron told a press conference as a summit of the 28 EU leaders broke up.

Under pressure from growing eurosceptic sentiment and dissent within his own Conservative Party, three years ago the Prime Minister promised an in-out referendum by 2017 but said he would campaign to stay in if he won key powers back from Brussels.

It is widely expected that he will call the vote for June.

Cameron said Britain would be "permanently" outside of the EU's advance towards an "ever closer union," and it would never join the euro bloc.

It would also have the right to challenge any development in the eurozone which threatened the pound and its economic interests, he said.

Cameron said the EU would also now focus more efforts on improving its economic competitiveness by slashing red-tape and boosting trade ties with major economies around the world.

The benefits to Britain would be huge, at billions of pounds (dollars, euros) a year, he said.

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