Russia operated a state-sponsored doping programme at the Sochi Winter Olympics in 2014, claims a new report.
An investigation commissioned by the World Anti-Doping Agency says Russia's sports ministry "directed, controlled and oversaw" the manipulation of urine samples provided by its athletes.
The commission looked into allegations made by the former head of Russia's national anti-doping laboratory.
Grigory Rodchenkov claimed he doped dozens of athletes before the Games.
The commission was led by Dr Richard McLaren, a Canadian law professor and sports lawyer who said he had "unwavering confidence" in his findings.
Rodchenkov also alleged he had been helped by the Russian secret service.
He claimed they had worked out how to open and reseal the supposedly tamper-proof bottles that were used for storing urine samples so the contents could be replaced with "clean" urine.
To prove this allegation, McLaren sent a random amount of samples from "protected Russian athletes" at Sochi 2014 stored by the anti-doping laboratory in Lausanne to another in London to see if they had scratch marks around the necks of the bottles that would indicate they had been manipulated.
McLaren said "100% of the bottles had been scratched" but added that this would "not have been visible to the untrained eye".
The damning report will fuel calls for a complete ban on Russia from the 2016 Summer Olympic, which start in Rio de Janeiro in Brazil on 5 August