David Cameron says he has secured "explicit commitments" to protect the integrity of the EU single market in negotiations to resolve the eurozone crisis in Brussels.
Mr Cameron said that leaders of the 17 eurozone states made "important steps forward" during talks which stretched through Thursday night, and now appeared to recognise how much further they need to go in the direction of closer economic and fiscal union.
But he said that nothing which the eurozone does to stabilise its currency should impact on the single market, which should remain a matter for all 27 EU states.
Financial markets rose on Friday morning in response to the lifeline for the eurozone's tottering banks agreed in the early hours after Italian prime minister Mario Monti and Spain's Mariano Rajoy faced down Germany's chancellor Angela Merkel in a tense summit showdown between eurozone leaders.
Mrs Merkel had come to the summit insisting that there were no short-term fixes on the table. But she was forced to relent after Mr Monti and Mr Rajoy - with the backing of French president Francois Hollande - made clear they would block any further progress if they did not receive assistance to curb their soaring borrowing rates.
At a press conference at the conclusion of the summit, Mr Cameron welcomed the deal. "There is more to do, but they have made some important steps forward," he said.
"In the longer term, the eurozone - like any single currency - needs closer economic and fiscal integration to secure its future: the remorseless logic that I have spoken about. These are difficult decisions but I believe all the countries now recognise how much more needs to be done."
Mr Cameron said he had objected to the inclusion of references to economic and monetary union (EMU) in a growth compact discussed at the summit.
He said: "While Britain wants this done, it has to be achieved in a way that doesn't distort the single market. For us that's the cornerstone of the EU and the biggest benefit we get out of membership. Three million British jobs depend on that market being open and working for us.
"In the conclusion today, I secured explicit commitment that, as this work deepening EMU goes ahead, the integrity of the single market will be fully respected. It was tough securing this, but absolutely vital, so that as this work proceeds it goes ahead in a way that protects our interests."