France overwhelmingly rejected the European Union's constitution in a referendum on Sunday, pollsters' projections showed, plunging the EU into crisis and dealing a possibly fatal blow to a pact designed to make it run smoothly.

The heavy defeat dreaded by EU leaders could weaken France in the 25-member bloc, stall European integration and unsettle some financial markets. It also wounds President Jacques Chirac two years before presidential and parliamentary elections.

Projections by three polling groups based on partial results from the referendum suggested around 55 percent of voters had opposed the EU's first constitution, designed to simplify decision-making following the Union's enlargement last year.

Such a heavy defeat in a country that has long been one of the main pillars of the EU reduces the chances of a repeat vote, which French leaders had ruled out anyway before the referendum.