Sancho was missing from the United squad for Sunday's dramatic defeat at Arsenal, and after the game Ten Hag said the forward was omitted as a disciplinary measure.
“Jadon, on his performances in training we did not select him,” Ten Hag told reporters.
“You have to reach a level every day at Manchester United and we can make choices in the front line. So for this game he was not selected.”
But Sancho has emphatically denied his level of effort in training was a concern, insisting his manager's claims are "completely untrue", adding that he has been made a "scapegoat for a long time".
In a statement posted on Twitter, he said: "Please don't believe everything you read! I will not allow people saying things that is completely untrue.
"I have conducted myself in training very well this week. I believe there are other reasons for this matter that I won't go into, I have been a scapegoat for a long time which isn't fair! All I want to do is play football with a smile on my face and contribute to my team.
"I respect all decisions that are made by the coaching staff, I play with fantastic players and grateful to do so which I know every week is a challenge. I will continue to fight for this badge no matter what!"
Antony started at the Emirates, with Alejandro Garnacho coming off the bench in the second half. Sancho is yet to start a game for United this season, but has come off the bench in all three so far.