Florencio rode for the Bouygues Telecom team in the 2008 Tour
Spain's Xavier Florencio has been pulled out of the 2010 Tour de France by his Cervelo Test Team for using a product containing a banned substance.
The 30-year-old treated saddle sores with a product containing ephedrine without consulting the Cervelo doctor.
"The team has immediately withdrawn him due to a violation of internal policies," said a team statement.
Cervelo's team contains 2008 Tour de France champion Carlos Sastre and Britons Jeremy Hunt and Daniel Lloyd.
Norway's Thor Hushovd, who pipped Britain's Mark Cavendish to win the green points jersey on last year's Tour, is also part of the Cervelo team.
It is not yet clear whether Florencio will be replaced in the team and Cervelo could start the Tour, which gets under way with a prologue stage in Rotterdam on Saturday, with eight riders instead of the usual nine.
The statement continued: "Consistent with the team's internal values, Test Team riders are required to obtain permission from the team's medical staff before they can use any supplements or medication.
"Xavier Florencio has been using a substance containing ephedrine to treat a saddle discomfort. This substance was not cleared in advance with the medical staff. This usage without clearance violates the internal policy.
"The rider is suspended from competition until the team can make a final determination based on all the facts. At this point there is no information yet on whether the rider can or will be replaced."
Cycling has been dogged by doping scandals in recent years and on the eve of this year's event, disgraced 2006 Tour winner Floyd Landis has raised the issue again.
Speaking to the Wall Street Journal, the former US Postal rider has spoken of blood transfusions taken during races - one on an isolated Alpine mountain and another in a hotel room during the 2004 Tour.
Landis has also made fresh claims that the team had funded their doping operation by selling off spare bicycles.
Three other former US Postal riders, who were not identified, had said in interviews that doping had occurred within the team, the Journal added, but all the riders and officials identified by Landis have denied the accusations.
Among those questioning the accusations is seven-time Tour de France winner Lance Armstrong.
"Landis's credibility is like a carton of sour milk: once you take the first sip, you don't have to drink the rest to know it has all gone bad," he said in a statement.
Armstrong has often been accused by his rivals and critics of cheating but has never failed a doping test and has always maintained his innocence.