Wiggins a great example of a clean rider

The head of the UCI has praised the 2009 Tour de France as the cleanest for several years, citing the threat of a four-year ban and improvements in testing as evidence.

Pat McQuaid said that the riders were ‘bombarded’ with tests which meant the risk of being caught was too great.

The four-year ban, brought in at the start of this year, is clamping down on the number of riders using performance-boosting drugs, said McQuaid.

He highlighted Bradley Wiggins, currently third in the overall standings, as evidence a clean rider can do well.

"Wiggins is a very, very strong anti-doping advocate," McQuaid said, who admitted that Lance Armstrong, tested as many as three times in two days, had been targeted alongside his Astana team-mate Alberto Contador as they were among the top riders.

McQuaid also praised the new ‘passport’ scheme which can signal changes in a rider’s blood.

“The database is a very strong weapon in our armoury," McQuaid said. "If a rider goes into a doping regime, experts will see evidence of tampering. The athletes don't really know what we can see."

After 11 scandals from the past two races, including the expulsion of the 2007 race leader Michael Rasmussen for missing tests, 15 of the 21 stages this year have yet to yield any positive results. In 2006, Floyd Landis became the first Tour winner to lose his title for doping.

Wiggins, who finished 124th in the 2006 Tour, is attempting to become the first British cyclist to secure a top-three finish. He has spoken out against riders who failed drug tests, including Alexandre Vinokourov, who tested positive for blood doping at the 2007 Tour.

The Briton's Cofidis team withdrew after a team-mate tested positive in that year's race, and Wiggins then said he had been close to quitting as a result. He said the 2007 Tour had "lost all credibility".