BRUSSELS, Belgium -- Cyclist Frank Schleck was suspended until July 14 by Luxembourg anti-doping authorities for testing positive to a banned substance during last year's Tour de France.

The RadioShack Nissan Trek leader was given a 12-month suspension backdated to last year's Tour, where he tested positive for the diuretic Xipamide, Luxembourg Anti-Doping Agency president Robert Schuler said on Wednesday. Schleck 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 on July 17, five stages from the end.

The suspension means Schleck will miss this year's Tour.

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

Schleck was facing up to a two-year suspension but the Luxembourg anti-doping authorities shied away from that.

"The fact that he never was condemned and never tested positive during the countless doping controls he underwent, allows the disciplinary council to consider that a 12-month suspension is proportional," the ruling said.

Schleck's team said it would study the verdict before announcing further steps and possibly appeal to the Lausanne-based Court of Arbitration for Sport. The World Anti-Doping Agency and the International Cycling Union can also appeal to seek a tougher sentence.

Frank and his brother Andy have been Luxembourg's most popular cyclists over the past decade. Andy Schleck was awarded the 2010 Tour 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 UCI 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.

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. WADA 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.