The war of words between Lance Armstrong and the US Anti-Doping Agency intensified after the Dutch newspaper De Telegraaf named five former team-mates of the Texan at the US Postal Service team as having given evidence to the anti-doping body. Usada issued a statement saying: "No individual cases have been finalised and any attempt to guess at whom potential witnesses might be only leads to inaccurate information being reported and subjects those named to unnecessary scrutiny, threats and intimidation."

Armstrong, seven times a Tour de France winner, has always denied use of performance-enhancing drugs and he responded by attacking the investigation.

"So let me get this straight… come in and tell them exactly what they wanted to hear and you get complete immunity AND anonymity? I never got that offer. This isn't about [Usada CEO Tyson] Tygart wanting to clean up cycling; rather it's just a plain ol' selective prosecution that reeks of vendetta."

Since it was revealed in mid-June that Armstrong faced formal doping charges speculation has been intense over the identity of the 10 witnesses cited by Usada in its case against the Texan and how their evidence was obtained. His five former team-mates named as having given evidence are present on the Tour de France.

David Zabriskie and Christian Vande Velde are racing here for the Garmin-Sharp team, which is directed by another former Armstrong team-mate Jonathan Vaughters, while the other two cyclists named are the overall contender Levi Leipheimer, who races for Omega-Pharma Quick-Step, and the veteran George Hincapie, who rides with Cadel Evans at BMC.

Reports that the riders have been offered six-month suspensions for doping offences in a deal for providing evidence against Armstrong were strongly denied by Vaughters on Thursday, who said that, as far as his riders were concerned, "the report of any six-month suspensions is completely untrue". He did, however, say in a statement that riders with the Garmin-Sharp team were expected to cooperate with anti-doping bodies if asked to.

Leipheimer and Hincapie were asked about the allegations at the start of Thursday's fifth stage of the Tour from Rouen to Saint-Quentin. Leipheimer said: "I'm 100% focused on this race; that's all I have to say. I can't say anything, I'm not going to comment." A spokesman for his Omega-Pharma Quick-Step team said they needed more evidence about the allegations. "We have to know the truth but it's something that is not related to our team."

Hincapie also refused direct comment, saying: "I'm just disappointed with this thing being brought up once again. I feel like I've always done the right thing for the sport." Asked whether he has spoken to Armstrong recently, Hincapie added: "I haven't in a while. I feel bad that he's going through all this. Lance has done so many things for the sport. His accomplishments are incredible, what he's achieved in the sport of cycling, the attention he brought to the sport of cycling, what he's done for cancer in society is honourable."

All five named rode with Armstrong at US Postal Service in the early 2000s. Last month Hincapie, Leipheimer, Vande Velde and Zabriskie chose not to be considered for the United States Olympic team.