The foul-mouthed radio personality launched into a rant about The Tonight Show host during an interview with British newsman Piers Morgan on his new CNN talk show.
Stern insists Leno is not as good as rival TV star David Letterman, and claims the comedian relies on others to provide his gags.
He tells Morgan, "Jay is insane. And Jay is a crook. And the world knows exactly what he's up to. He steals a tremendous amount of material. He's not fit to scrub David Letterman's feet. I don't know how he's beaten David Letterman in the ratings. It's beyond my comprehension. America must be filled with morons who at night lay in bed - the ones who are watching him, they must be in a coma...
"This guy's ripped off like 10 major things from my show."
The Piers Morgan Tonight show featuring Stern airs in America on Tuesday night (18Jan11).