BERLIN - Anti-doping controls at the Beijing Games will be the most extensive ever implemented, said International Olympic Committee (IOC) vice president Thomas Bach.

Bach, the head of Germany's National Olympic Committee who is also chairman of the IOC's disciplinary commission, said anti-doping screening had improved since scandals plagued the 2004 Athens Summer Games and the 2006 Turin Winter Olympics.

"The Beijing Games will be by far the most rigorously controlled ever and the most stringently controlled multi-sport event ever," said Bach.

"We've taken a big step forward. There has been a lot of movement forward in the battle against doping."

It is not only an increase in doping checks, up to 4,500 in Beijing from 3,600 in Athens, but also more sophisticated testing, stiffer punishments and the special attention competitors will get for any conspicuous behaviour.

"The developments are continuing and you can see changes in products and substances being used. We've reacted to that," said Bach, 54.

"If there are any positive tests it will show the system is working."

GOLD MEDAL

Bach, a trained lawyer who won a fencing gold medal for West Germany at the 1976 Olympics, added Germany and other countries had vowed to exclude anyone violating anti-doping rules from their next Games teams.

Possession of a prohibited substance constitutes a violation of the rules and athletes can now be tested more than once a day, he said.

In Germany, Olympians are required to sign anti-doping pledges and face stiff financial penalties for infringements.

"The overwhelming majority of the athletes are clean," Bach said. "The aim is to ensure they can have full confidence in an authentic competition."