Mo Farah's coach Salazar and training partner Rupp hit back at doping claims

A BBC documentary on Wednesday alleged that Salazar, a former marathon runner who has become one of the most famous running coaches in the world, has been involved in violating anti-doping rules - and further alleged that he was involved in Rupp being "given the banned anabolic steroid testosterone in 2002, when he was 16 years old.”

There is no suggestion that Farah is involved in any wrongdoing.

In a statement on Wednesday, Salazar said the BBC and U.S. website ProPublica had engaged in "inaccurate and unfounded journalism".

"I believe in a clean sport and hard work and so do my athletes," said Salazar. "Apparently that is not interesting enough for some.

"I am very disappointed that the BBC and ProPublica and their 'reporters' who have allowed themselves to be used by individuals with agendas and have engaged in such inaccurate and unfounded journalism.

"Rather than present the facts, they opted for sensationalism and innuendo."

The United States Anti-Doping Agency (USADA) would not comment on whether Salazar's group was under investigation.

Rupp has found fame chiefly as the training partner of British double Olympic champion Farah, and the image of him cheering Farah on to 10,000m glory at London 2012 while also collecting silver himself has become the stuff of athletics legend.

He has denied ever using performance enhancing drugs.

"I expressly told these reporters that these allegations were not true and their sources admit they have no evidence, yet they print 'suspicions' attacking me and sullying my reputation," said Rupp in an e-mailed statement.

"That is inexcusable, irresponsible journalism."

A World Anti-Doping Agency spokesman said the agency had viewed the BBC programme and that any investigation would be up to USADA and the International Association of Athletics Federations.

"We acknowledge that the programme also raises questions regarding the ability of athletes to dope by taking minimal amounts of performance enhancing substances without testing positive, otherwise known as 'micro-dosing,'" WADA said in a statement.

"It is an issue that we are exploring in great detail with experts."

The BBC has yet to provide further evidence beyond the Panorama documentary, but in a follow-up article the BBC's Mark Daly claims that, "for more than a year I have been investigating this story, collaborating with the US Investigative journalism outfit ProPublica.

"The allegations range from the abuse of banned steroids, to subverting the Therapeutic Use Exemption (TUE) process, in which an athlete can apply to use a banned drug or method if there is a genuine medical need. If proved, both offences would result in lengthy bans.

"Salazar, who strenuously denies any wrongdoing, is also accused of giving athletes prescription medications that they either did not need or were not prescribed in the hope that a competitive advantage could be gained. Alberto Salazar and Galen Rupp were invited to be interviewed. They declined but provided statements."

Daly also speaks about the famous 'Oregon Project', the Nike-funded training camp run by Salazar, whose methods have been credited with turning Farah from a talented youngster into a near-unbeatable big-race winner.

Salazar himself dreamt up the Oregon Project, which opened its doors in 2001 - with Rupp the key athlete who had been spotted at the time.

"I wanted to start the Oregon Project with the best available professional runners, but ultimately, Galen was going to be the star," Salazar said in his autobiography, as cited by Daly's BBC article.