The agent at the centre of the Daily Telegraph investigation into Justin Gatlin's entourage has claimed he made up his comments about obtaining banned drugs to impress the undercover reporters.

Robert Wagner, who occasionally represents the reigning world 100 metres champion, and Gatlin's former coach Dennis Mitchell were secretly filmed by the newspaper claiming they could obtain and administer human growth hormone and testosterone.

The newspaper's reporters had gone to meet the pair at Gatlin's Florida training base and had posed as producers interested in making a film about a sprinter - the drugs were meant to help the film's lead actor get into shape.

Mitchell and Wagner said they would get the drugs from a doctor in Austria and bring them into the country for $250,000 and they also suggested doping was still rife in athletics.

But, in a statement by a British-based public relations company, Wagner said the newspaper's story is "deeply flawed" because it is based on false comments he made up to impress people he thought were in the film business.

"It was just big talk - I did not actually source or supply the substances the reporters asked for but stupidly claimed I could," the US-based Austrian said.

"I apologise to Mr Gatlin, his management and family for saying completely false things about him and I apologise to other completely innocent athletes also wrongly implicated by my words."

Wagner added that he reported his meeting with the reporters to the Athletics Integrity Unit (AIU), the new anti-doping and corruption body set up by the sport's governing body the IAAF, a month ago and will assist the investigation it has started "in every way I can".

According to his "athlete representative" profile on the USA Track and Field website, Wagner looks after eight US athletes, including Olympic 400m hurdles champion Dalilah Muhammad and triple jumper Imani Oliver, who was given a one-year ban by the United States Anti-Doping Agency (USADA) in May.

Earlier on Tuesday, Gatlin posted a statement on his Instagram account saying he was "shocked and surprised" when he learned Mitchell had allegedly offered to supply performance-enhancing drugs.

"I am not using and have not used PEDs (performance-enhancing drugs)," wrote Gatlin, who has twice served doping bans during a controversial career.

"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 and I will not allow others to lie about me like this."

The AIU and USADA issued statements on Monday night to confirm they are working together on an investigation into the newspaper's claims, and IAAF president Lord Coe described the allegations as "extremely serious".

Gatlin won 100m gold at the World Championships in London this summer, triumphing over Usain Bolt.

His victory was greeted by boos from the crowd - a response he has become used to after serving bans in 2001 and 2006, although he has also denied intentional doping.

According to the Telegraph, Gatlin was not present when Mitchell and Wagner discussed banned drugs with the reporters.

Mitchell, an Olympic sprint relay champion who served a two-year doping ban during his track career, has also strongly denied any wrongdoing.

The Telegraph have been asked for a response to Wagner's statement but the investigative team behind the sting have not replied.