However, UEFA said the study did not provide "any scientific evidence" of potential doping in football.

The broadcaster said that along with the British Sunday Times newspaper it had seen the study conducted by 12 European anti-doping labs where more than 4,000 urine samples from about 900 top players between 2008 and 2013, mainly from the European leagues, were tested.

ARD, which said the samples were anonymous, will screen its full program on Sunday.

A total of 68 players returned samples that showed conspicuous levels of testosterone, the broadcaster said, which represented a percentage of 7.7 compared to 1.3 percent of conspicuous levels in older tests.

Higher levels of testosterone can occur naturally in some cases but can also be the result of doping.

"This study does not present any scientific evidence of potential doping in football especially due to the presence of confounding factors, the lack of standardisation procedures among the 12 laboratories and the quantification of steroid profiles when the samples were collected," said UEFA in a statement to Reuters.

"Furthermore, there was an inability to perform a second analysis [B sample] as required now by the WADA international standards for laboratories."

"The study simply shows that the introduction of steroidal biological passport in football would be beneficial by offering further analysis possibilities in case of atypical test results.

"UEFA has had a very thorough anti-doping program for many years with over 2,000 tests a year and only two occurrence of positive tests, both for recreational drugs, which proves that doping in football is extremely rare."

The German broadcaster and the English newspaper had claimed in August the world athletics body IAAF had failed to follow up on hundreds of suspicious doping tests, prompting the launch of an investigation with results expected in November.

Reuters