Justin Gatlin's previous drugs tests are to be re-run in the light of a Telegraph investigation, sources have revealed.

The 100 metre world champion has been dragged into a fresh doping scandal after members of his entourage offered to supply performance enhancing drugs to undercover reporters.

The Prime Minister said that she was "extremely concerned" about the revelations, adding that athletes must "compete on a level playing field".

It also led to calls for the FBI to investigate, with Damian Collins, the Chairman of the Culture, Media and Sport select committee, saying that an investigation by law enforcement "could be the only way to crack doping in sport".

Mr Gatlin, his coach Dennis Mitchell and Robert Wagner, an agent connected to him, are already being investigated by the Athletics Integrity Unit (AIU) and the US Anti-Doping Agency (Usada).

A source close to the investigation said: “We have a retesting policy that has been in place for some time now. We know that this is a game of catch up, and with world champion or a gold medalist we have a lot of their samples stored for retesting.”