China's top backstroke swimmer Ouyang Kunpeng has been banned for life for doping, officials confirmed on Friday, dealing the host nation an embarrassing blow just 42 days before the start of the Beijing [Images] Olympics [Images].

Chinese swimmers were embroiled in a series of doping scandals in the 1990s and the country's sporting authorities have pledged to weed out drug cheats before the Beijing Olympics.

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First time offenders usually receive a two-year ban so Ouyang's tough sentence will serve as a stern warning to any other Chinese drug cheats before the Aug. 8-24 Games.

The 25-year-old tested positive for the anabolic agent clenbuterol, Zhao Jian, head of the anti-doping office at the Chinese Olympic Committee (COC) confirmed.

Ouyang, a semi-finallist at the 2004 Athens Olympics and winner of four silver medals at the 2006 Asian Games, claimed the 100 and 200m titles at the national championships in April and was his country's best hope of an Olympic backstroke medal.

"The swimmer Ouyang Kunpeng tested positive in an out-of-competition test on May 1," read an official Chinese Swimming Association (CSA) notice posted on the website of the official China Sports Daily paper.

"The Chinese Swimming Association decided to give him a life ban ... although we have done lots of work, this positive case still happened, which is a big lesson for us.

"We are going to take a clear stand on anti-doping work and firmly crack down on any violations."

His coach Feng Shangbao has also been banned for life, the notice said.

Ouyang is the biggest-name Chinese swimmer to fail a dope test for several years, although the suspicions of systematic doping that accompanied the country's sudden emergence as a swimming power have proved hard to erase.

NOTORIOUS CASE

In the most notorious case, four Chinese swimmers failed pre-competition doping tests for the diuretic triamterene before 1998 world championships in Perth.

Another female swimmer, Yuan Yuan, and her coach, Zhou Zhewen, were disqualified from the championships after being caught with 13 vials of the muscle-building human growth hormone at Sydney airport.

The decline in doping cases has been coincided with a drop-off in China's success in international competition and they came away from last year's world championships in Melbourne with just one silver and a bronze.

Chinese sports officials have consistently said they would rather win no gold medals at the Beijing Games than have a single doping case.

Last year, China conducted 10,238 tests, in and out of competition, and uncovered 15 positive samples, seven of them from weightlifters.

All Chinese athletes selected for the Beijing Olympics will be screened for banned substances before the Games with violators strictly and publicly punished, Zhao said last year.

World Anti-Doping Agency chief John Fahey visited China in April and said he had witnessed a "clear will" for a clean Games.

The International Olympic Committee has promised to conduct the strictest drug testing regime for any Games in Beijing. Some 4,500 tests will be conducted, up from 3,600 in Athens.