WARSAW -- Polish President Aleksander Kwasniewski said he was worried that the country's economic stagnation may hurt turnout at next year's referendum on European Union membership, a newspaper reported on Saturday.

Kwasniewski -- a leftist who won a second term of office in 2000 said he would propose a bill in September to allow Parliament to declare the referendum valid if its turnout slips below a minimum 50-percent constitutional threshold.

"Any political, social or economic crisis in Poland ... may trigger negative views toward European Union membership," Kwasniewski was quoted as saying by the *** Rzeczpospolita *** daily.

"There is no basis for crisis talk ... but there still may appear some frustration which may lower the referendum turnout," he said. The poll is expected to be held in autumn, 2003.

June polls showed EU support in Poland -- the largest of 10 mainly Eastern European nations seeking EU membership in 2004 -- falling by three points to 57 percent as the country battles the worst economic slowdown in a decade and record dole queues.

Poland has a history of low voter turnout. Only 46 percent of the electorate participated in general elections last year, reflecting growing frustration over the ability of democratically elected representatives to ease social pain.

Kwasniewski called for government action to thwart growing support for anti-European parties, such as the populist Self-Defense Party of maverick leader Andrzej Lepper, who has made his name with street protests and Brussels-bashing rhetoric.

"EU opponents speak out loudly, and that requires action on our part," Kwasniewski said. "But with people like Lepper we cannot hold this discussion only through television video clips," he added, referring to the government's EU publicity campaign.

Though polls still show a three-to-one majority of Poles favor joining the EU, Poland's two Eurosceptic parties now claim backing from nearly a quarter of voters in the nation of 38.6 million.

On Thursday EU Enlargement Commissioner Guenter Verheugen said Poland should face down opponents of its bid to join the bloc -- a priority for Poland's left-wing coalition government -- or risk political isolation and economic crisis.

Prime Minister Leszek Miller has already staked the future of his government on the referendum by announcing in April that his cabinet would resign if Poles reject EU membership next year, Reuters said.