More than a third of Olympic and world championships medals - including 55 golds - have been won by athletes with suspicious doping test results, the "biggest leak of blood-test data in sporting history" reportedly reveals.
It also suggests that at least 800 athletes - one in seven of those named in the files - have recorded blood-test results described by an expert as "highly suggestive of doping or at the very least abnormal", according to the Sunday Times.
Another allegation is that more than a third of the world's fastest times in endurance events were recorded by athletes whose tests have triggered suspicion.
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The newspaper says it, along with the German broadcaster ARD/WDR, has had access to a database containing more than 12,000 blood tests from 5,000 athletes and which it claims reveals "the extraordinary extent of cheating by athletes at the world's most prestigious events".
The data, which belongs to the IAAF but was released by a whistleblower, has been analysed by two leading anti-doping experts for the Sunday Times - scientist Robin Parisotto and exercise physiologist Michael Ashenden.
According to them, the leaked information reveals that more than a third of medals have been won in endurance events at the Olympics and world championships by athletes who have recorded suspicious tests.
The newspaper claims none of those medals has been taken away by the authorities.
It is also alleged that a top UK athlete is among seven Britons with "suspicious" blood scores, while 10 medals were won at the London 2012 Olympics by athletes who have reportedly recorded dubious test results.
Mr Parisotto said: "Never have I seen such an alarmingly abnormal set of blood values. So many athletes appear to have doped with impunity and it is damning that the IAAF appears to have idly sat by and let this happen."
Mr Ashenden was also critical of the IAAF, saying: "For the IAAF to have harvested millions of dollars from the broadcasting of athletics events around the world ... yet only devote a relative pittance of those funds towards anti-doping, when they could see the terrible truth of what lay beneath the surface, is ... a shameful betrayal of their primary duty to police their sport and to protect clean athletes."