BRUSSELS, Dec 14 (Reuters) - The European Union’s ambitious drive for a constitution to strengthen integration lay in ruins on Sunday just five months before the bloc is set to expand into eastern Europe.

Poland and the Czech Republic warned against Franco-German talk of pressing ahead with a “two-speed Europe” while Britain said the breakdown of negotiations to devise a new rulebook for a union of 25 nations would have little effect.

EU leaders on Saturday aborted a summit due to approve the landmark charter — two years in the making — when a clash over voting power pitting giants France and Germany against Spain and Poland proved insuperable.

Diplomats said Polish Prime Minister Leszek Miller rejected a final offer to delay the introduction of a reformed voting system until 2014, prompting France, Germany and Britain to call a premature end to the negotiations.

Some leaders fear the EU now faces a crisis of governance. French President Jacques Chirac said a “pioneer group” of states may forge ahead with closer integration in economics, defence and crime-fighting. But Poland cautioned against this.

“Our philosophy in the discussion is for the enlarged Union to develop jointly, with the same speed over the entire area and not only among the chosen ones,” Polish President Aleksandr Kwasniewski told a news conference.

The summit breakdown capped a traumatic year in which Europeans were bitterly split over war in Iraq, EU budget rules were bent, Sweden voted against joining the euro and Britain delayed indefinitely a referendum on the same question.

Most leaders avoided open recrimination in the aftermath of the debacle, but the blame game started in the European media with some pointing the finger at Italian Prime Minister Silvio Berlusconi, whose country holds the rotating EU presidency.—Reuters