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.

"The French people have given a huge smack in the face to an entire system that has the nerve to tell us what to think," said nationalist French politician Philippe de Villiers, a leading opponent of the charter. "The constitution is no more."

Chirac swiftly conceded defeat in a televised address to the nation as the "No" camp celebrated a crushing victory with about 55 percent of votes to 45 percent and hinted that he might respond by dismissing his unpopular prime minister.