Boonen was caught speeding under the influence of alcohol last week
Former world champion Tom Boonen will not be allowed to compete at next month's Tour de France after testing positive for cocaine.
Boonen, who tested positive on 26 May, is under investigation in his native Belgium for cocaine possession.
Race director Christian Prudhomme said: "Tom Boonen is a big champion but a big champion must also be exemplary. The integrity of the Tour could be harmed."
Boonen's Quick Step team will be allowed to compete in the event.
The 27-year-old sprinter had said that he would "accept the consequences".
"I am not going to defend myself here, but I have caused my family, friends and team pain and I apologise for that," said Boonen, who has also been excluded from the Tour of Switzerland, which starts on Saturday.
"I have been in the news in a negative way lately. I am not perfect and will accept the consequences."
Sprint specialist Boonen was not charged and was released on Monday after questioning by authorities in Turnhout, Belgium, over the test results.
After discussions with the sponsor we decided to reconfirm our trust in Tom Boonen
Quick Step manager Patrick Lefevre
Belgian police, who carried out a series of searches, found no further evidence against him.
On Tuesday the International Cycling Union (UCI) told BBC Sport that the Quick Step rider would not face punishment from them as the test came out of competition.
UCI spokesman Enrico Carpani said that, regardless of the results, he was unlikely to have to answer to the sport's governing body.
"If Boonen is tested positive for cocaine, it's not a sports problem," he said.
"There is no violation as, in out-of-competition tests, cocaine is not a forbidden substance for the World Anti-Doping Agency (Wada) code and UCI anti-doping rules."
Carpani confirmed that the three days before a race is considered out of competition and that the UCI had not been officially notified of the drugs test.
Wada classifies cocaine as a stimulant on the official prohibited list but it is only prohibited if the substance is taken during competition, spokesman Frederic Donze said.
Boonen ran into further trouble with police last week when he was caught speeding while under the influence of alcohol.
Quick Step manager Patrick Lefevre said that the sprinter had a future with the team.
"After discussions with the sponsor we decided to reconfirm our trust in Tom Boonen," Lefevre said.
"The easiest thing is to dump someone if they did something wrong. We know the athlete Tom Boonen has done a lot for our team in the last six years and we hope in the coming three years he can still do more for the team."