President Vladimir Putin has called the whistle-blower who has provided evidence of what investigators say was an elaborate state-sponsored doping program a "jerk" who should not be trusted.
Putin made the comments on January 30 after a German television documentary quoted Grigory Rodchenkov as saying that the Russian president must have been aware of the doping program.
"They've got this jerk, Rodchenkov," Putin said, apparently referring to the United States, where he is under witness protection.
"Everything is based on the statements by this man who can hardly be trusted in any way," Putin said.
Putin said that it's partially Russia's "own fault" for being under scrutiny for doping. "After all, there were instances of doping use," he added.
Putin has repeatedly denied state involvement in doping and claimed Rodchenkov forged doping evidence against Russian athletes at the behest of "foreign" forces.
In an ARD documentary aired on January 29, Rodchenkov said Russia's doping program "came right from the top, from the president. Because only the president can appoint the domestic secret service FSB for such a specific task."
The former director of Russia's anti-doping laboratory also confirmed the content of secret documents that, according to ARD, say that state-organized doping practices existed for the 2008 Olympics in Beijing and London 2012.
In May 2016, he described in an interview to The New York Times an elaborate doping scheme that he said involved dozens of Russian athletes at the 2014 Sochi Olympics.
Earlier on January 30, Putin's spokesman Dmitry Peskov dismissed Rodchenkov's claims as "yet more slander which doesn't have a single piece of evidence to support it."
"Mr. Rodchenkov is a wanted man, he is under investigation," Peskov said. "He is an odious individual who has problems with the law."
Russian prosecutors have accused him of being largely responsible for the doping scandal.
Rodchenkov organized the Russian system of doping before fleeing to the United States in 2016 and providing evidence of it to the World Anti-Doping Agency (WADA) and Canadian lawyer Richard McLaren, who led a WADA-commissioned investigation.
The International Olympic Committee (IOC) suspended Russia in August 2016 as a result of the probe.
McLaren confirmed many of Rodchenkov's allegations in his reports, and an IOC panel said in November that Rodchenkov was a "truthful witness."
With reporting by AFP and TASS