French voters have rejected the proposed EU constitution in Sunday's referendum, according to an exit poll.
The poll quoted by French TV gives the "No" side 55% - in line with surveys published in the run-up to the vote.
If confirmed, the result will be a blow to President Jacques Chirac and France's two main political parties, which campaigned for a "Yes".
It could deal a fatal blow to the EU constitution, which the Union has been working on since the start of 2002.
The constitution cannot come into force unless it is ratified by all 25 EU members.