As one of the leading members of the goalkeeping union, Banks' defence of De Gea's weak punch in the 1-1 draw with Spurs, which led to Clint Dempsey's equaliser, comes as no surprise, but he believes the United players should be encouraging, rather than lambasting their team-mate.
Banks told Press Association Sport: "I was very upset to hear Gary Neville talking about how the players were disgusted with him (De Gea), how they were looking at him, after he hadn't punched the ball quite clear enough.
"I thought to myself, `hang on a minute, it's not just the goalkeeper that makes mistakes, everybody makes mistakes in football matches'.
"I couldn't quite believe that, because if anything he would've liked a bit of a lift: `come on, get your head up'. I found that a bit strange that he (Neville) was saying they'd go back in the dressing room and give him a telling off."
De Gea has been the subject of scrutiny for some time after moving from Atletico Madrid to succeed Edwin van der Sar as United's first-choice stopper.
Banks is impressed with some aspects of the 22-year-old's game and encouraged him to work on his weaknesses - dealing with crosses and through balls.
"He's got very good reflexes, makes excellent saves you think other goalkeepers probably wouldn't have got," added Banks, who feels sympathy for goalkeepers trying to stop the modern ball.
"He's got lots of years left yet. What he needs to do is to practice on the crosses as much as he possibly can. I used to practice on my weaker things as much as I possibly could and it certainly did help me.
"It's much more difficult for a goalkeeper playing in today's game. The ball is moving all over the place. For me, that ball has taken a lot of the art of goalkeeping out of the game. I do feel sorry for goalkeepers today."