Welsh 800m runner Gareth Warburton has been ruled out of the Commonwealth Games in Glasgow after being suspended from competition by UK Athletics for committing an anti-doping violation.
The 31 year old, who represented Great Britain at the London 2012 Olympic Games, faces a maximum two year ban if found guilty at a hearing before the national anti-doping panel at a date yet to be decided.
Warburton said in a statement: "The news of this anti-doping rule violation has come as a great shock to me.
"From the outset, I would like to state that I have not knowingly taken any banned substance. As a professional athlete, I have always supported and have been an advocate of clean sport. Nothing has changed in this regard.
"However, I recognise that the responsibility for this situation lies with me and I'm committed to working with UK Anti-Doping and will fully cooperate in the legal process."
The Team Wales athlete finished fourth in Delhi in 2010 but it is yet unknown where he will next appear on the track.
"UK Athletics has today announced that 800m athlete Gareth Warburton has been provisionally suspended from all competition after being charged with committing anti-doping rule violations under UK Athletics Anti-Doping Rules," a UK Athletics statement read.
"The athlete has the opportunity to respond to the charges against him, and to have those charges determined at a full hearing before the National Anti-Doping Panel."
The news comes as the World Anti-Doping Agency confirm that life bans for doping offences cannot be legally enforced. Former 100m world record hold Asafa Powell has recently seen his 18-month ban cut to six months.
"Our advice was that [life bans] would be challenged and would not be sustainable in law," Wada president Sir Craig Reedie told BBC Sport.
"A four-year penalty will stand up in court and takes a person out of the cycle of an Olympic Games. Not many athletes dope on their own. There is usually someone else involved, be it a coach, friend, manager or agent."