Justin Gatlin says he is "shocked and surprised" at claims his coach offered to supply an undercover reporter with performance enhancing drugs.
The Daily Telegraph alleged that Gatlin's coach Dennis Mitchell and an athletics agent, Robert Wagner, had offered to supply banned drugs for an actor training for a film.
But in a short statement the 100m world champion has denied any wrongdoing himself and confirmed earlier reports that Mitchell was no longer in his employ.
"I am not using and have not used PED's," he said. "I was shocked and surprised to learn that my coach would have anything to do with even the appearance of these current accusations. I fired him as soon as I found out about this.
"All legal options are on the table as I will not allow others to lie about me like this. I have no further comments as it is now a legal matter. They will next hear from my lawyer."
Undercover reporters visited Gatlin's Florida training camp and they claim Mitchell and Wagner offered to supply and administer testosterone and human growth hormone.
They were also secretly recorded claiming that the use of banned drugs in athletics was still widespread.
The United States Anti-Doping Agency and the Athletics Integrity Unit, the new body set up by athletics' world governing body the IAAF to oversee all anti-doping matters in the sport, are investigating the allegations.
Usada said in a statement: "Investigations stemming from tips and whistleblowers play a critical role in anti-doping efforts.
"We are presently coordinating with the Athletics Integrity Unit in order to investigate these claims fully. As with all investigations, we encourage individuals with information to come forward as an important tool to help protect clean athletes. Importantly, individuals are innocent unless and until the established process determines otherwise. It's only fair to let due process occur before jumping to any conclusions."
Brett Clothier, head of the AIU, said in a statement: "These allegations are very serious and strike at the heart of the integrity of athletics. The IAAF anti-doping code and code of conduct applies not just to athletes, but also athlete support personnel. The Athletics Integrity Unit will be investigating this matter in co-operation with USADA and we hope the Daily Telegraph will provide information to assist.
"The use of new methodologies and designer drugs has always been a challenge for the anti-doping movement and this continues to this day. In this era, we understand that we cannot rely on testing alone to defend the sport against doping and so the AIU is both building its investigations and intelligence capability and implementing an intelligence based re-testing policy to meet such challenges."
IAAF president Lord Coe, described the allegations as "extremely serious".
Gatlin, who has twice served doping bans, beat Usain Bolt to claim gold in August, the 35-year-old's victory roundly greeted by boos from the crowd at the London Stadium.
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