A former San Francisco supervisor pleaded guilty to three felony charges Friday and admitted to trying to shake down city business owners with planning permit problems.

Ed Jew resigned from the Board of Supervisors in January after a federal grand jury indicted him on charges that he demanded $80,000 from owners of outlets of the Quickly chain of fast-food restaurants to help them solve their permit issues.

During an FBI sting in 2007, agents videotaped the owners delivering a $40,000 payment to Jew in marked $100 bills and promised to pay the rest later. Agents found $10,000 of that cash wrapped in foil and stored in a freezer during a raid of his Burlingame home.

After changing his story several times, Jew told the FBI that he gave $20,000 to a consultant and kept the other half. Jew said he intended to donate much of it to charity while keeping the rest to buy hot dogs and hamburgers for community events.

"Even though the money was to be used for projects in my district, taking it was illegal at the time, and I knew it," Jew said in court Friday. He blamed his "inexperience and naivete and lessons taught by other politicians" for contributing to his downfall.

Jew, 48, was elected to the board in 2006.

He remained free pending a Feb. 13 sentencing hearing. He faces a maximum of 20 years in prison, but his clean criminal record will probably get him a much shorter prison sentence.

Jew has pleaded not guilty to separate state election fraud charges that he lied about living in San Francisco to qualify to represent the city's western neighborhoods.