Double Olympic champion Mo Farah has issued a statement denying he has ever taken performance-enhancing drugs.
Farah has spoken out after reports emerged claiming he missed two drugs tests prior to the London 2012 Olympics, at which he won gold in the 10,000 and 5,000 metres.
Those claims also came soon after a TV documentary alleged that Farah's coach Alberto Salazar had been involved in doping.
Farah has not been accused of doing anything wrong, and nor is there any sanction for missing two drugs tests as censure would be invoked after three.
But the 32-year-old has felt the need to put some words on the record.
In a statement issued via Facebook, Farah wrote: "I have never taken performance-enhancing drugs in my life and I never will.
"Over the course of my career I have taken hundreds of drugs tests and every single one has been negative. I've fully explained the only two tests in my career that I have ever missed, which the authorities understood, and there was never any suggestion that these were anything more than simple mistakes.
"The last two weeks have been the toughest of my life - with rumours and speculation about me that are completely false - and the impact this has had on my family and friends has left me angry, frustrated and upset.
"In particular, the media pressure on my young family and my wife, who is five months pregnant, is extremely painful, especially as I'm away training for some important races."
Salazar has denied the allegations against him, which focused on another athlete in his stable, Galen Rupp.
Farah has also spoken to Salazar, who is based in Oregon, about the matter.
He added: "As I made clear, I went to Portland to speak to Alberto Salazar and demand answers. He reassured me that the claims are false and that he will soon be providing evidence to make that clear. Until then I will not be commenting further on the allegations.
"I would like to take this opportunity to thank my fans, family, friends and team-mates for all the great support they have provided over the last few days and hope that I will now be allowed to focus on my training and winning medals for my country."