The legendary United centre-back is never far from developments at his former club and was disgusted after watching Ten Hag's side comfortablybeaten 3-0 at Old Trafford on Sunday.
A dismal performance saw Brennan Johnson, Dejan Kulusevski and Dominic Solanke all score without reply as United slumped to a third defeat of the new Premier League season.
Defeat leaves the club 12th in the league standings and already eight points behind leaders Liverpool who are continuing to make significant progress under their new boss Arne Slot.
Rio Ferdinand questioned 'what the hell are' Manchester United after Sunday's defeat against Spurs
Analysing United's torrid outing, Ferdinand criticised his former employer's defence as they allowed Spurs defender Micky van de Ven to run almost the length of the pitch before pulling the ball back for Johnson to score the first goal.
Ferdinand was shocked at the team's overall play and questioned 'what the hell' United are under Ten Hag.
'We'll get to the red card in a minute but Van de Ven ran through the whole team and I look at it, happened midweek as well,' Ferdinand said in a video on X.
'Where's the pride man? I just don't know. That fight don't seem where it should be. The Bruno red card I think is p*** poor as well. I think it's a p*** poor red card.
'In no day and age should that ever be a red card. A straight red card? No way, I can't have it,' he added.
'But do not let that distract from the fact that we were terrible. We were an embarrassment today. The red card shouldn't be an excuse for anybody at Man Utd now. It shouldn't be an excuse for anyone at the football club,' he added.
'We were terrible. We were terrible to watch. It was a terrible kind of representation of who were are and what we are right now.
'Giving the ball away constantly. I'm ranting here but I can't help it. I've sat and watched the game and just thought what the hell are we?' Ferdinand further fumed.
Meanwhile, United are expected to appeal against Fernandes' red card that saw the club captain given his marching orders for a rash challenge on midfielder James Maddison.
Fernandes appeared to be slipping at the time when he made the challenge that caught the Tottenham midfielder on the shin.