China's top backstroke swimmer Ouyang Kunpeng has been banned for life for a doping offense just 42 days before the start of the Beijing Olympics. The Chinese Swimming Association (CSA) confirmed on Friday Ouyang had tested positive for an illegal substance, dealing the Olympic host nation an embarrassing blow. Chinese swimmers were embroiled in a series of doping scandals in the 1990s but the country's sporting authorities had pledged to weed out drug cheats before the Beijing Games. The 25-year-old Ouyang won three individual silver medals at the 2006 Asian Games and three golds at the 2003 world university games. A CSA spokesman confirmed the positive test and said an official notice had been posted on the website of the official China Sports Daily paper. "The swimmer Ouyang Kunpeng tested positive in an out-of-competition test on May 1," it read. His coach Feng Shangbao has also been banned for life.