Wiggins: I considered quitting cycling

Wiggins' Cofidis team were withdrawn from the Tour earlier this week after team-mate Christian Moreni failed a drugs test and was questioned by police.

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And Wiggins told a news conference in Manchester today: "My initial reaction was 'I'm going to get out of the sport'. It was sheer anger but once I settled down a bit, I'm willing to see this thing through.

"So far on this tour five people have spoiled it out of nearly 200 who started in London.

"I've had no regrets that I still wasn't there. It's not a nice place to be. The whole thing has just completely lost credibility as far as I'm concerned."

On Wednesday Tour leader Michael Rasmussen was sacked by his Rabobank team and thus removed from the race for his failure to inform them of his whereabouts in the build-up to the Tour.

The Dane's dismissal heaped further scandal on a race already reeling from the expulsions of Italian Moreni and pre-race favourite Alexandre Vinokourov of Kazakhstan, who had failed dope tests.

Vinokourov's Astana team also withdrew from the race.

Olympic champion Wiggins, 27, believes a minority of competitors have undermined the whole event.

"The start in London was amazing but things slowly started deteriorating," he said.

"The whole thing is null and void this year as far as I'm concerned.

"Five riders have tarnished the sport and tarnished the Tour de France. It's wrong to say everyone is doing it.

"I'm not bitter but I am angered by it. It has made me determined to come through this whole thing and prove that there can be clean winners in this sport. That made my determination even stronger."

Wiggins believes the older generation of riders are more likely to risk doping.

He said: "A minority are willing to push the boundaries. [Some of the] older guys that were back there in 1998 are still willing to push the boundaries and see how far they can go without being caught.

"I think it's a generation thing," he said.