Welsh 800m runner Gareth Warburton has protested his innocence after being served with a provisional suspension for an alleged doping offence.
The 32-year-old had been due to compete at his third Commonwealth Games in Glasgow this month before being informed of his suspension by UK Athletics.
A statement from UK Athletics read: "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 (presence of prohibited substances).
"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."
Warburton finished fourth in the 800m at the Commonwealth Games in Delhi in 2010 and had hoped to go one better after being named in the Wales squad.
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.
"I'd like to take this opportunity to wish the best to all my team-mates heading to the Commonwealth Games and apologise that I won't be able to join them as part of Team Wales."
Warburton holds two medals from the European Indoor Championships and was also part of the Great Britain team at London 2012, where he failed to qualify from his first round heat.
Team Wales Chef de Mission Brian Davies said: "Team Wales can confirm that one of the competitors selected for the Glasgow 2014 Commonwealth Games has been provisionally suspended after being charged with committing an anti-doping rule violation. As a result Gareth Warburton will no longer be able to compete at the Games.
"As the athlete is presumed innocent unless and until the charges brought against him have been upheld it would be inappropriate for us to comment further.
"Team Wales is committed to providing athletes with the necessary education required to ensure we compete as clean athletes at a clean Games, and have worked closed with UK Anti-Doping in the build-up to Glasgow 2014."