Gordon Brown clashed with Nicolas Sarkozy, the French President, over the remit of a new group of senior figures who will look at the long-term future of the European Union.
The Prime Minister claimed victory after a summit of EU leaders ruled out further changes to their institutions "for the foreseeable future". He insisted there was no appetite for another treaty after a six-year wrangle to secure the Treaty of Lisbon signed on Thursday.
But Mr Brown stopped short of ruling out any further EU integration and M. Sarkozy provided ammunition for British Eurosceptics by suggesting the new group described as "wise men" would consider such moves. He said the group, proposed by France, would discuss "a politically integrated Europe" and "what will be the new [European] dream".
The French President also differed with Mr Brown by saying that the "wise men" could consider whether the EU could continue to expand "indefinitely". That revived fears that France might try to use it to block Turkey joining the EU club, even though EU enlargement is outside the group's formal remit.
Britain claimed it had watered down a French proposal to include support for protectionist measures in a summit statement on the global economy which broadly endorsed Mr Brown's free trade vision.
Another row between the two nations is looming over closer EU co-operation on defence, which M. Sarkozy will push when France takes over the EU's rotating presidency in July.
The "wise men" group will be chaired by Felipe Gonzalez, the former Spanish prime minister. Mr Brown is lobbying to secure a place on it for Richard Lambert, the CBI director general.
He brushed off criticism by Peter Mandelson, Brit-ain's European Commissioner, who told the BBC he should make Europe a higher priority. Mr Brown replied: "Europe is a very big priority."