Double Olympic champion Mo Farah has reiterated that he has never taken performance enhancing drugs, and explained that the two drugs tests he has missed in his career were "simple mistakes".

Farah, who won the 5000 and 10000 metres at the 2012 Olympic Games in London, was reported by the Daily Mail to have missed two tests in the build-up to those triumphs at his home Olympics.

It was claimed that the long-distance runner first missed a test in early 2010 - before he joined coach Alberto Salazar - with the second instance said to have taken place in 2011, when it is claimed Farah could not hear his doorbell when testers went to his home.

At that time athletes were permitted to miss three tests in an 18-month period before a four-year ban could be imposed.

The claims follow a BBC documentary in which doping allegations were made against Salazar and Farah's training partner Galen Rupp - who won silver in the 10000m in London - although both men have the denied any wrongdoing.

Farah, who is set to return to the track at the Diamond League meeting in Monaco next month, has now moved to explain his missed drugs tests.

"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," he said in a statement.

"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."

Farah stated earlier this month that he would not stop working with Salazar, and revealed he has been to visit his coach to discuss the claims made against him.

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."