Mo Farah insists he has never taken performance-enhancing drugs and "never will" in a statement released on his official Facebook page.
The double Olympic champion also claimed the last few weeks have been the "toughest in his life" and left him "angry, frustrated and upset".
Alberto Salazar, Farah's coach, has been at the centre of recent doping allegations - along with training partner Galen Rupp - but both deny any wrongdoing.
Farah, who has not been accused of anything illegal, has come under scrutiny after a report in the Daily Mail claimed he missed two drugs tests in the build-up to the London 2012 Olympics, where he won 5,000 and 10,000m gold.
But he said: "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 had earlier denied suggestions his relationship with Farah had broken down, and the Briton said he had been "reassured" by his coach that the allegations are false.
Farah added: "As I made clear, I went to Portland to speak to 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 teammates 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."