David Howman, the director-general of the World Anti-Doping Agency, believes that it is wrong for Lance Armstrong to take "centre stage" at this year's Tour de France.

Armstrong, who had all seven of his Tour de France triumphs scrapped after his use of performance-enhancing drugs, is taking part in a charity ride organised by former footballer Geoff Thomas to try to help raise £1m to help fight blood cancer.

Riders will start a day earlier than the beginning of the race, but Howman has insisted that focus will be taken away from the 102nd edition of the event.

Howman is quoted by BBC Sport as saying: "It's disappointing Armstrong should take centre stage in an event which he cheated in so often.

"He's welcome to try to save lives. I don't think he should be ambush marketing an event which is far superior to what he is doing."

Armstrong's frequent use of performance-enhancing drugs led to him being banned from all professional sport in 2012.