Prime Minister Leszek Miller and
his wife Aleksandra cast their vote

Prime Minister Leszek Miller, whose minority cabinet's future depends on a strong 'Yes' vote, was among the first to cast a ballot on Saturday morning.

"This is one of the biggest days in Polish history. I hope Poles will today choose the best path for Poland and for the future of all of us," Miller told reporters.

Surveys suggest that three in four Polish voters will vote for EU acceptance.

But government officials fear that apathy could keep turnout below 50 percent – the minimum amount needed for the result to be binding in the largest of 10 countries invited to join the EU in 2004.

If less than half the electorate cast their votes, the referendum will be deemed invalid and parliament will have to decide the issue by a two-thirds majority.

This could shake up financial markets and unseat Prime Minister Leszek Miller's unpopular government.

Support varies

Support for EU membership variesa among Polish citizens. City dwellers, who are among the most prosperous of Poles, are the largest supporters of EU entry.

But poor farmers, small retail traders, and workers of nearly bankrupt state-owned corporations tend to be euro-sceptic or apathetic.

"Nothing will change for me if we join the EU. But will have to listen to orders from Brussels. I voted 'No'," said Jozef Knapik, who owns a small semi-subsistence farm in the southern
village of Cianowice, after casting his ballot.

His neighbour, Marian Molik disagreed: "I grow blackcurrants and much of it goes to Germany. I am in favour of the EU, because I'll be able to sell more blackcurrants there."

About 25,000 polling stations opened at 0400 GMT. First-day turnout figures will be released after they close at 1800 GMT, and first exit polls were expected shortly after voting ends at 1800 GMT on Sunday.

The blandly run pro-EU campaign has been helped by appeals to vote "Yes" from Polish-born Pope John Paul, UK Premier Tony Blair and German Chancellor Gerhard Schroeder.

Malta, Slovenia, Hungary, Lithuania and Slovakia have all voted to join the EU, but turnout in Slovakia barely cleared a similar 50 percent minimum. The Czech Republic, Estonia and
Latvia have yet to vote.