Tour de France leader Michael Rasmussen has admitted making a mistake in missing out-of-competition drugs tests.
Rasmussen has held the yellow jersey since last Sunday
But the Dane insists he backs moves to make cycling drug-free.
"I'm sorry the situation is coming out now, when I'm wearing the yellow jersey, and it's harming the sport that I dearly love," he said.
"I want to make absolutely clear I've had out-of-competition tests prior to the Tour de France, 14 tests during the Tour and all the results are negative."
The Rabobank rider added: "I do support my team in the fight against doping and [for] a clean sport."
He has either been unprofessional or has used the system
The Danish Cycling Union said last week Rasmussen had been warned for missing two random controls earlier this year and banned him from September's world championships and the 2008 Olympic Games.
It later emerged he had already been warned twice by the International Cycling Union (UCI) for missing two separate random tests in the past 18 months.
Rabobank manager Theo de Rooy said he was aware of the missed tests and revealed he fined Rasmussen 10,000 Euros (£6,720).
"I informed the UCI about the missed tests prior to the Tour de France, and UCI president Pat McQuaid has said that they could not prevent Michael Rasmussen from racing on the Tour," said De Rooy.
"For me, there is no case to answer."
As part of Tour de France policy, the race leader is tested after each stage and Rasmussen has worn yellow since his breakaway win in Tignes last Sunday.
Rasmussen has claimed he simply made an "administrative error" in forgetting to inform anti-doping testers of his whereabouts when they were looking for him.
British rider David Millar, who has been a vocal opponent of drug use since he was banned for two years for using blood-booster EPO, spoke out on the issue in French newspaper L'Equipe on Monday.
"It is unacceptable that Rasmussen did not give notice of his whereabouts," said Millar.
"He started the race knowing what would happen but did nothing to rectify the situation and now we are all screwed.
"It is understandable he had problems communicating his address from Mexico, but it is up to him to make sure his federation receives notification.
"He has either been unprofessional or has used the system."
The Tour resumes on Wednesday with the final Pyrenean stage, covering 218.5 km and including three major climbs.
Rasmussen holds a lead of two minutes 23 seconds over Alberto Contador, now considered his only serious rival for victory in Paris on Sunday.
Meanwhile, the T-Mobile team will discover at the end of the race on Sunday if the German mobile telephone operator will withdraw their sponsorship.
"We will consider things and make a decision at the end of this year's race," said the company's communications director Christian Frommert.
The company has a contract to sponsor the team until 2010 but the sport's image has taken a hit in Germany after details of T-Mobile rider Patrik Sinkewitz failed drugs test emerged last week.
Sinkewitz could still be cleared of having elevated levels of testosterone via a B test.