CHICAGO – Illinois is among the top five states with the highest frequency of contaminated beaches and Chicago has one of the most polluted beaches in the nation, according to a new report from the Natural Resources Defense Council.

Jackson Park’s 63rd Street Beach in Chicago was cited in the council’s report released Tuesday as one of the six most polluted beaches in the country.

The national study, based on federal Environmental Protection Agency data, found there were 591 beach closings and advisory days in Illinois last year. That’s a slight increase from the 584 closing days or advisories in 2005. At the 63rd Street Beach, swim bans or advisories were issued on 35 days between Memorial Day and Labor Day last year, according to the report.

Ellen Sargent, the Chicago Park District’s deputy director of natural resources, said the city’s aggressive E. coli testing of its beaches most likely results in more closings and advisories than at other beaches around the country.

“They’re not comparing apples to apples, so it’s unfortunate that all of the aggressive … testing at our beaches is now in question,” Sargent said.

Nationwide, there were more than 25,000 closing or advisory days.

The report blamed most of the problems on increased stormwater washing pollutants into waterways.

Other states the report cited with the most often contaminated beaches were Ohio, Indiana, Rhode Island and Minnesota.

“It’s clear we still have a long way to go,” said Ann Alexander, an attorney for the group that released the study. “We should be holding developers accountable along the lake for how they build their developments and make sure they’re providing green space.”