Jan. 5 (Bloomberg) -- China, the world’s biggest Internet market by users, announced a nationwide crackdown on Web sites that it says spread pornography, singling out search engines including Google and Baidu for criticism.

China’s Ministry of Public Security and six other government agencies jointly opened a one-month campaign at a meeting today in Beijing. The central government announced the decision through an official Xinhua News Agency report posted on its Web site.

A vulgar tone on the Internet has seriously damaged the physical and mental health of youth, Cai Ming-zhao, deputy press chief of the State Council, said at the meeting. Participants asked all related government agencies to “strictly execute the law,” Xinhua said.

Web sites that refuse to change after receiving warnings risk penalties and closure, Xinhua said.

Baidu and Google, China’s biggest search engines, provide links to “a huge quantity of pornographic sites,” according to a statement from the China Internet Illegal Information Center today. Sina Corp., the biggest Chinese Web portal, was accused of hosting “tawdry” blog and photo sites, according to the center, which is linked to the Ministry of Civil Affairs.

Google Inc. is owner of the world’s most-used search engine. Baidu Inc. is China’s most popular search engine.

Linda Sun, a Beijing-based spokeswoman for Baidu, and Cathy Peng, for Sina, declined to comment. Google spokeswoman Marsha Wang didn’t immediately answer calls to her mobile phone seeking comment.

The center said a total of 16 other Web sites operated by companies including Sohu.com Inc., Tencent Holdings Ltd., and NetEase.com Inc. hosted “harmful” information.

To contact the reporter on this story: James Peng in Hong Kong at jpeng7@bloomberg.net; Mark Lee in Hong Kong at wlee37@bloomberg.net.

Last Updated: January 5, 2009 04:48 EST