Athletics is set to be engulfed in a fresh doping crisis following the "biggest leak of blood-test data in sporting history", the Sunday Times reports.
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.
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According to them, the leaked data reveals that more than a third of medals - including 55 golds - 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 have 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.
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Among the other claims, the Sunday Times says more than 800 athletes - one in seven of those named in the files - have recorded blood-test results described by one of the experts as "highly suggestive of doping or at the very least abnormal"; and that more than a third of the world's fastest times in endurance events were recorded by athletes whose tests have triggered suspicion.
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."
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."
The IAAF has so far been unavailable for comment when contacted by Press Association Sport.
The World Anti-Doping Agency (Wada) said it was "very alarmed" by the latest claims which would "shake the foundation" of clean athletes across the globe.
The ARD documentary, Doping - Top Secret: The Shadowy World Of Athletics, contains new allegations regarding widespread doping in international athletics.
Wada president Sir Craig Reedie said: "Wada is very disturbed by these new allegations that have been raised by ARD; which will, once again, shake the foundation of clean athletes worldwide."
He also announced that given the nature of the allegations, they would be handed over immediately to the organisation's Independent Commission for further investigation.
"These allegations require swift and close scrutiny to determine whether there have in fact been breaches under the World Anti-Doping Code and, if so, what actions are required to be taken by Wada and/or other bodies."
"As always, Wada is committed to doing what's necessary to ensure a level playing field for clean athletes of the world."