Mo Farah’s coach Alberto Salazar is facing further scrutiny after it emerged that a leaked United States Anti-Doping Agency report suggested that he failed to establish a valid reason for possessing testosterone and committed “unlawful” behaviour by rubbing a gel containing the banned substance on his sons.

The interim Usada report – which was leaked by the Russian hackers Fancy Bears – also raises “suspicions and concerns” about Salazar’s practice of giving Galen Rupp personal massages before big races, despite Nike employing massage therapists, a story broken in 2015 by the Guardian.

According to the BBC, Farah also remains under investigation over an alleged 2014 infusion of the legal supplement L-carnitine and whether it breached the legal limit of 50ml. He strenuously denies breaking any rules and has called upon Usada to publish its evidence. Insiders at British Athletics have told the Guardian that Farah’s infusion was well below the legal limit.

Even so, these latest revelations are sure to increase the pressure on British Athletics, who have stood loyally by the legendary endurance coach ever since the BBC’s Panorama suggested that he may have committed anti-doping violations two years ago.

Salazar has never hidden the fact that he carries testosterone gel with him, but claims it is because he suffers from hypogonadism, which means he suffers from low testosterone and requires testosterone replacement therapy. Yet the Usada report dismisses this explanation, saying that Salazar failed to provide “acceptable justification for possessing testosterone”.

“Despite Usada’s request that he do so, Mr Salazar has still produced no laboratory testing records, blood test data, examination notes, chart notes or differential diagnosis substantiating that Mr Salazar suffers from hypogonadism,” it adds.

Rule 21.2.6 of the World Anti-Doping Agency code states that athlete support personnel are strictly banned from possessing banned drugs without “valid justification.”

Salazar has also admitted conducting a testosterone experiment with Dr Jeffrey Brown, involving rubbing the banned substance on his sons, in a bid to see what levels would trigger a banned test. This, he explained in 2015, was to protect against his athletes potentially being sabotaged after a race so that they would test positive. Yet Usada are critical of this behaviour too, calling it “unlawful”.

On Sunday it was revealed that Usada’s report also says that Salazar “almost certainly” broke anti doping rules when he gave infusions of the amino acid L carnitine to six of his US athletes at the Nike Oregon Project in Portland, Oregon, where Farah trains.

The 269-page interim report, which was sent by Usada to the Texas Medical Board in March 2016 but never published, also alleged that Dr Brown had provided Salazar’s athletes with prescription drug cocktails, often with no medical need, and had “engaged in serial violations of professional, medical and ethical obligations to his patients, putting them at increased risk of injury to their health and wellbeing”.

On Thursday British Athletics performance director Neil Black maintained that Salazar would remain on their books unless Usada puts forward formal charges – pointing out that it would be wrong and unfair to make any assumptions without any evidence of guilt.

Salazar has always maintained his innocence, and issued a ferocious 12,000-word rebuttal to many of the allegations against him in 2015. On Sunday he released a statement which said: “I have clearly and repeatedly refuted allegations directed against me and the Oregon Project. I believe in a clean sport and a methodical, dedicated, approach to training. The Oregon Project will never permit doping.”