The England forward has been training with the club's academy players since accusing Erik ten Hag of lying over the reason for his omission from the squad for their defeat at Arsenal earlier this month.
After Sancho hit out at the Red Devils boss on social media, Ten Hag exiled the player from training with his teammates.
But it's now reported by the Daily Mirror that Sancho has also been barred from all first-team facilities at Man United's training ground at Carrington.
The report adds that Sancho isn't even allowed to eat with the first-team players at Man United and must dine alongside academy players instead.
Ten Hag has the backing of the club and Sancho will not be welcomed back until he apologises, talkSPORT understands.
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talkSPORT also understands that the Dutchman is not taking any satisfaction from the current situation.
Sancho was banished from first-team training following showdown talks with Ten Hag having not taken kindly to his manager's claim that he was left out of the squad for the 3-1 defeat to Arsenal as he didn't train well enough.
It's widely reported Sancho has refused to apologise and the 23-year-old has been totally frozen out. He was pictured watching Man United Under-18s at Carrington on the same day the first team were playing Brighton at Old Trafford.
It's understood a group of Man United players don't agree with the decision to banish Sancho, although Ten Hag poured cold water on those suggestions.
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Ten Hag said before Man United's win at Burnley last weekend: "I don't know if it's a leak but I know opinion, I know my players.
"Everyone can make suggestions, we are okay with it. At United, you have to win every game so it doesn't change anything. As always, it's about how we play against Burnley, there's no easy game, definitely not against Burnley."