Manchester City's Hart is widely considered as England's best goalkeeper at the moment but the 29-year-old had a time to forget during the 2016 European Championships where he make a number of high profile errors which ultimately cost the Three Lions.
As a result, there has understandably been a lot of media scrutiny on Hart currently and now former France international Barthez has also gone on to give a damning assessment of the City goalkeeper's abilities.
"His diving technique isn't good," the Frenchman said in an interview with Sport Witness.
"It's too horizontal, not aggressive enough.
"He messes up because he doesn't attack the ball's path, meaning his hands are then pushed back by the impact with the ball.
"Hart is two levels below (Manuel) Neuer, (Thibaut) Courtois and (Hugo) Lloris."