Ouyang Kunpeng, China's top backstroke swimmer, has dealt a blow to the notion that the host Olympic nation has ring-fenced its national team to avoid embarrassing doping scandals ahead of the Games in Beijing.

The swimmer has been banned for life by China after testing positive for the anabolic steroid clenbuterol. His coach, Feng Shangbao has also been banned for life. It is to be hoped that the swimmer and coach will help authorities trace the source of the banned substance back to the supplier.

The news comes just six weeks before the Games open in Beijing. After the scandals of the 1990s, when more than 40 Chinese swimmers tested positive, Beijing kept a tight control on its national team, ring-fencing many of its members in a controlled environment, either in the capital or within monitored groups in the provinces.

China's doping crisis came to a head when enough human growth hormone to supply the entire national team was found in the bags of swimmer Yuan Yuan by customs officers at Sydney airport in January 1998 as she made her way to the world championships in Perth. In the investigation that ensued, the Chinese Swimming Association admitted that it had no control over what was happening in the provinces.

In 2002, a plan was hatched to keep those likely to make the Olympic team in a ring-fenced environment at the national training centre in Beijing. Just as that would have at one time guaranteed that swimmers would come into contact with doping at a time when the head China coach was Zhou Ming subsequently banned for eight years), the idea was to keep swimmers and coaches away from suppliers and corrupt local officials. It has worked well to a large degree but Ouyang has now proven that the national team is not inaccessible to suppliers and rogues.

In a statement today, the Chinese Swimming Association said Ouyang tested positive on May 1. No 3 in the world in 2005 and among the top 15 in the world in 2006, he finished 11th in the 100m backstroke at the 2004 Olympic Games. Ouyang was not considered a medal contender in Beijing on recent form. In 2006, he won three silver medals at the Asian Games.

To its credit, the CSA, with an enormous task on its hands in terms of monitoring a nation that in the 1990s was awash with substances banned for sporting use, said: 'The Chinese Swimming Association has made lots of effort on anti-doping, however this positive test case still happened. It's a big lesson, and we need to stay alert on anti-doping and pay constant attention. The Chinese Swimming Association strongly opposes doping and is cracking down on doping to guarantee a fair-play environment, to protect athletes' health and guarantee athletes are clean when competing in Olympics.'

Chinese swimmers were involved in a series of doping scandals in the 1990s. In the past year, under pressure from the World Anti-Doping Agency, China has begun toughening its drug testing and is also trying to close factories in China that produce performance-enhancing drugs and sell over Web sites.

The China Anti-Doping Agency recently opened a new laboratory that will do 4,500 doping tests for the Olympics. This is up 25 per cent from Athens.

Last year, China conducted 10,238 anti-doping 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, according to Zhao Jian, head of the anti-doping office at the Chinese Olympic Committee.

In the past year, under pressure from WADA, China has begun to close factories in China that produce performance-enhancing drugs and sell them on the internet.