2007 Giro d'Italia winner
Danilo Di Luca is facing a lifetime ban from the sport after testing positive for EPO.
The Italian, 37, who was racing in this year's Giro d'Italia, has been sacked by his Vini Fantini-Selle team after failing an out-of-competition test.
Di Luca has already served a ban for
testing positive for the blood-boosting drug Cera at the Giro in 2009.
Vini Fantini team director Luca Scinto said: "Di Luca is an idiot. I never wanted him. He is sick and needs help."
Di Luca, who
only signed for the Italian team in April,
was ranked 26th in the race, 33 minutes, 33 seconds behind the leader Vincenzo Nibali.
In a statement from the Vini Fantini team, Scinto added: "Danilo Di Luca was not part of our group, was not wanted by the team and was inserted into our set-up by our main sponsor Valentino Sciotti, who out of friendship and regional ties to the rider, insisted upon and created the conditions for his addition to the roster.
"The good news is that it was an out-of-competition test so he was obviously targeted for a good reason and it shows that the testing is working.
"The bad news is that he was doing it in the first place but he's a serial doper and an idiot.
"It's hard not to tar everyone in his team with the same brush but you have to take each individual case on its merit.
"Di Luca was interviewed by the Italian press last week and he said what went on in the past, is in the past, but he's been lying to himself and I say good riddance to him"
"Following the news, which we received with disappointment this morning, the team fired the rider on the spot and told him to leave the race by his own means.
"At this point, Vini Fantini-Selle Italia will also open civil proceedings to claim damages from the rider, in accordance with the internal rules that all members of the team signed up to.
"I'm knocked out. I never wanted Di Luca in the team and didn't hide it, despite being criticised for my opinion.
"We made a mistake by accepting the repeated request from our main sponsor to have faith in a rider they are close friends with. Unfortunately this faith has been repaid with an incredible error."
Vini Fantini's main sponsor, Valentino Sciotti, admitted that Di Luca's place in the team was an error on his part.
"What can I say? I believed in the man and in the athlete and it is right that it should be me who takes the blame because I made a mistake," Sciotti declared.
"I must ask forgiveness from the fans, the team, the other sponsors, my partners and all the other cyclists who are racing in the Giro d' Italia fairly and honestly, and all those young athletes who will be shaken by this news."
Di Luca was quoted in the Italian newspaper La Gazzetta on Wednesday morning saying: "Doping is a weakness, period. But it's disappeared from cycling and other sports."
Giro race organisers announced the failed test on their official website saying it was carried out at Di Luca's home on 29 April, five days before the start of this year's race.
Giro d'Italia technical director Mauro Vegni told BBC Sport: "Di Luca has betrayed us and the Giro. I am of course unhappy but relieved it isn't a young rider. He belongs to a generation which has one foot in the doping camp."
The drug erythropoietin (EPO) improves endurance by increasing red blood cell production and oxygen transportation.
If the result is confirmed in a 'B' sample, Di Luca could face a lifetime ban as this is his third offence.
He received a two-year ban for his failed test at the 2009 Giro, which was subsequently reduced by nine months after he collaborated with Italian anti-doping authorities.
He was also banned for three months after winning the 2007 Giro for seeing a banned doctor.
It is the second doping case at this year's Giro after French rider Sylvain Georges tested positive for the banned stimulant Heptaminol in a urine sample after stage seven. The 28-year-old AG2R La Mondiale rider was immediately withdrawn from the race.