Luxembourg Anti-Doping Agency president Robert Schuler said that the RadioShack-Nissan-Trek team leader was given a 12-month suspension backdated to last year's Tour de France, where he tested positive for the diuretic Xipamide. He has denied any wrongdoing.

The 32-year-old Schleck placed third in the 2011 Tour de France and was in 12th place overall behind leader Bradley Wiggins when he stepped out of the race July 17, five stages from the end.

Schleck will miss this year's Tour de France and Giro d'Italia under the current suspension.

Wednesday's decision was the biggest doping ruling in the sport since Lance Armstrong admitted earlier this month he doped on his way to seven Tour de France victories.

Schleck was facing up to a two-year suspension. He can appeal to the Lausanne-based Court of Arbitration for Sport.

Frank and brother Andy have been Luxembourg's most popular cyclists over the past decade. Andy Schleck was awarded the 2010 Tour de France victory after Alberto Contador was stripped of the title because of a doping violation.

Frank won Alpine stages in the 2006 and 2009 Tours, and he also won the Amstel Gold Race one-day classic in 2006.

The International Cycling Union said the diuretic Xipamide turned up in a test conducted by the French anti-doping lab on a sample from Schleck taken on July 14, 2012.

The case at the time cast more doubt on cycling's ability to root out drug cheats despite vigorous controls put in place by the UCI and its allies.

The diuretic is classified as a specified substance and does not require a provisional suspension. The World Anti-Doping Agency defines specified substances as those that are "more susceptible to a credible, non-doping explanation." Bans for such substances are often shorter, and athletes have a better chance of proving that they did not intend to consume it or enhance their performance.