Arsenal and Chelsea have strongly denied reported claims made by a British doctor that players from both clubs were among 150 unnamed athletes he aided in taking performance-enhancing drugs, labelling them "false" and "without foundation".
The Sunday Times reported that London-based doctor Mark Bonar was secretly filmed stating he had provided athletes including footballers, cyclists and tennis players with banned substances.
The newspaper acknowledged it had no independent evidence of Bonar providing such treatment and has made no suggestion that any clubs had knowledge of the alleged wrongdoing.
Bonar is said to have told the newspaper he administered treatment to the athletes for medical reasons and not to enhance their performance. It has not been suggested the substances were illegal.
In response to the reports, an Arsenal statement read: "Arsenal Football Club is extremely disappointed by the publication of these false claims which are without foundation.
"The Sunday Times knows that these allegations are baseless but has preferred to publish regardless.
"The club takes its responsibilities in this area very seriously and our players are well aware of what is expected.
"We strictly adhere to all guidelines set by the World Anti-Doping Agency and our first team players participate in approximately 50 random drugs tests during each football season.
"None of our players has ever failed such a test."
Chelsea said in their own statement: "The claims The Sunday Times put to us are false and entirely without foundation.
"Chelsea Football Club has never used the services of Dr Bonar and has no knowledge or record of any of our players having been treated by him or using his services.
"We take the issue of performance-enhancing drugs in sport extremely seriously and comply fully with all anti-doping rules and regulations.
"Chelsea FC players are regularly and rigorously tested by the relevant authorities."