Daryl Impey denies wrongdoing tests positive for masking agent probenecid

Impey has been dropped by Orica-GreenEDGE after delivering a positive A and B sample during the South African Championships in February.

Probenecid is primarily used to treat gout, but also serves as a masking agent for anabolic steroids.

Impey led the Tour de France for two stages last year, but has not been included in GreenEDGE's nine-man squad for the 2014 race, which starts on Saturday.

But the 29-year-old insists he has no knowledge of taking the substance.

Impey said in a statement on his website: "Further to the announcement of the Tour de France team and in the interests of full disclosure, I confirm that on 23 June 2014, I was notified by William Newman, the President of Cycling South Africa, about an adverse analytical finding for probenecid following an in-competition test at the national time trial championships on 6 February 2014.

"I had no knowledge of probenecid nor have I ever taken the substance knowingly in any manner. I am committed to drug-free sport and fully intend to take all steps necessary to clear myself of any suspicion.

"The notification came as a complete shock to me just days before the start of the Tour de France, particularly since anti-doping tests conducted on me on 8 and 9 February 2014 yielded no adverse results.

"I immediately flew back to South Africa and was present at the analysis of my B sample on 27 June 2014, the results of which confirmed the initial analysis.

"I am extremely distressed by the finding, as I have always raced clean throughout my career. Every result that I have achieved to date has been as a result of hard work and dedication on my part.

"I notified my team immediately after being informed by Cycling South Africa of the adverse finding. I would like to thank them, my family and friends for their support during this difficult time. I remain confident that I will be vindicated and proved innocent of any wrongdoing."