Farah was questioned by Usada officials for nearly five hours - and Panorama has obtained a transcript of that interview.
Asked specifically and multiple times whether he had an L-carnitine injection before the London Marathon, Farah repeatedly denied it.
He was asked: "If someone said that you were taking L-carnitine injections, are they not telling the truth?"
Farah said: "Definitely not telling the truth, 100%. I've never taken L-carnitine injections at all."
He is then asked: "Are you sure that Alberto Salazar hasn't recommended that you take L-carnitine injections?"
Farah responds: "No, I've never taken L-carnitine injections."
He is asked again: "You're absolutely sure that you didn't have a doctor put a butterfly needle… into your arm… and inject L-carnitine a few days before the London marathon?"
Farah says: "No. No chance."
We have learned that minutes after the interview, Farah then met Fudge, who had been interviewed by Usada the day before.
Farah then rushed back in as the investigators were packing up. He changed his account.
Farah tells Usada: "So I just wanted to come clear, sorry guys, and I did take it at the time and I thought I didn't…"
He is asked: "So you received L-carnitine… before the London marathon?"
Farah answers: "Yeah."
He adds: "There was a lot of talk before… and Alberto's always thinking about 'What's the best thing?' 'What's the best thing?'"
The Usada investigator says "… a few days before the race… with… Alberto present and your doctor and Barry Fudge and you're telling us all about that now but you didn't remember any of that when I… kept asking you about this?"
Farah responds: "It all comes back for me, but at the time I didn't remember."
Mo Farah declined to be interviewed by Panorama.