SEOUL — A popular online critic of President Lee Myung-bak who rose to national fame with a podcast lampooning the South Korean leader was thrown into prison Monday after he was convicted of spreading false rumors connecting Mr. Lee to allegations of stock fraud.

The Web celebrity, Chung Bong-ju, 51, was one of the four co-hosts of “Naneun Ggomsuda,” or “I Am a Petty-Minded Creep.” Since it began in April, the weekly online talk show has drawn a nationwide audience and become one of the world's most downloaded political podcasts from the Apple iTunes store.

The show, the first of its kind in South Korea, was titled after a nickname for the president that is popular among his most vocal critics. Mr. Chung and his co-hosts have reveled in satirizing Mr. Lee and bringing up allegations against him and other political and economic leaders of a kind that South Koreans usually do not encounter in their country’s mainstream news media.

Last Thursday, the Supreme Court upheld a lower-court verdict that had sentenced Mr. Chung to a year in prison. The ruling said he had violated the country’s election and defamation laws when he spread unconfirmed rumors that Mr. Lee had been implicated in a stock scandal ahead of the December 2007 presidential election. Mr. Chung was a national lawmaker when he made the statements.