The International Association of Athletics Federations (IAAF) has been accused of blocking a study which showed as many as a third of the world's top athletes violating anti-doping rules, but the association denied it on Sunday.
The University of Tubingen in Germany is reported to have said that the world athletics governing body blocked publication of the study, Sunday Times reported on Saturday.
Hundreds of athletes apparently told researchers in 2011 that they had cheated. The IAAF said discussions were going on about the report's publication.
In a statement to the newspaper, the university said: "The study is an independently initiated scientific research project and was not commissioned by the IAAF. The IAAF's delaying publication for so long without good reason is a serious encroachment on the freedom of publication."
The governing body responded saying: "Discussions are ongoing with the research team and WADA (the World Anti-Doping Agency - the other partner in the project) regarding publication of the study."
Four years ago, a team of academic researchers interviewed hundreds of athletes at the World Championships in Daegu, South Korea. The Sunday Times reported the study concluded that 29 to 34 percent of the 1,800 competitors at the championships had violated anti-doping rules.
It said that a month after collecting the information, the researchers were told to sign a confidentiality agreement to prevent them speaking out about the admissions.
A leaked copy of the full study has been seen by the Sunday Times. "These findings demonstrate that doping is remarkably widespread among elite athletes, and remains largely unchecked despite current biological testing programmes," the newspaper concluded.
The findings are similar to the newspaper's revelations a fortnight ago after it obtained access to the results of 12,000 blood tests from 5,000 athletes.
Two leading anti-doping experts found that, between 2001 and 2012, a third of medals, including 55 golds, were won in endurance events in the Olympics and World Championships by athletes who have recorded suspicious tests.
However, denying the accusations IAAF said it had "never vetoed publication of this article."
It added in a statement: "This is not a new story, having first been raised on German TV in 2013."
