Doping allegations continue to mar the world of cycling, as a champion of the sport's most prestigious race has been stripped of his title.

Alberto Contador has lost his 2010 yellow jersey, making him the second Tour de France winner-turned-loser after being found guilty of using a banned substance.

The Spanish cyclist was also suspended for two years after the Court of Arbitration for Sport ruled that he had ingested clenbuterol – a stimulant similar to ephedrine used to increase one's heart rate.

Contador had claimed that he tested positive for clenbuterol after eating contaminated meat.

Last year, a Spanish cycling tribunal decided to exonerate Contador. The International Cycling Union and World Anti-Doping Agency responded by launching appeals.

The CAS upheld those appeals on Monday, saying in a ruling that, "The presence of clenbuterol was more likely caused by the ingestion of a contaminated food supplement."

Contador's suspension makes him the second Tour de France champion to have his title stripped for doping. American Floyd Landis lost his 2006 title after testing positive for testosterone.

Andy Schleck of Luxembourg finished behind Contador at the 2010 Tour de France and will be retroactively credited with the victory. The Spaniard, meanwhile, will also be stripped of his 2011 Giro d'Italia victory.

Schleck finished 39 seconds behind Contador in 2010 but said being elevated to champion will not bring him happiness.

"I feel sad for Alberto. I always believed in his innocence. This is just a very sad day for cycling," Schleck told The Associated Press. "The only positive news is that there is a verdict after 566 days of uncertainty. We can finally move on."

Cycling legend Eddy Merckx weighed in on the controversy as well, saying on Monday that cycling was receiving unfair scrutiny compared to other sports.

"Cycling always receives a bad name. It's always cycling that's attacked and other sports are never attacked. In other sports they don't go so far," Merckx said. "If you go zero-zero-zero-zero-zero (tolerance) you can always find something in everyone."

He said the decision represents a significant blow to cycling's international reputation.

"It's very bad for cycling. It's bad for everybody. It's like someone wants to kill cycling," Merckx told The Associated Press at the Tour of Qatar. "I'm very surprised, very surprised. It's bad for the sponsors. It's bad for the Tour (de France). It's bad for cycling.

Contador had previously won the Tour de France in 2007 and 2009. He is one of only five cyclists to have won the Tour de France, the Giro d'Italia (in 2008) and the Spanish Vuelta (in 2008).

Because the CAS backdated his suspension, he is eligible to return to competitive cycling on Aug. 6, meaning he will miss the Giro d'Italia, the Tour de France and the 2012 Olympics in London.

He would be eligible to return for the Spanish Vuelta, however, as that race gets underway on Aug. 18.

Contador has blamed a steak he had purchased from a Basque producer for containing the banned substance. Clenbuteral is sometimes used to fatten livestock.

The CAS ruled that while the contaminated meat scenario was possible, it also wasn't likely. Instead it concluded there were no established facts to support his theory, noting that no other athletes had tested positive for clenbuteral due to the consumption of Spanish meat.

International Cycling Union president Pat McQuaid described the decision as a "sad day for our sport."

"There are no winners when it comes to the issue of doping: every case, irrespective of its characteristics, is always a case too many," McQuaid said.

Contador tested positive during a rest day on July 21, 2010, but the results were not confirmed publicly two months later when he was suspended pending an investigation.

In February 2011, the Spanish cycling federation cleared Contador of the allegations and Spanish Prime Minister Jose Luis Rodriguez Zapatero spoke out in defence of the national icon.

The International Cycling Union and World Anti-Doping Agency appealed, ultimately leading to Monday's decision and the two-year ban.

The CAS said it would consider a request to fine Contador US$3.25 million.

With files from The Associated Press