Grammy-winner Legend, 33, said that the former Disney stars are not singers, reported Ace Showbiz.
"You know it's interesting. It should be very interesting. I don't have much to say. It's interesting when people, you know, are judging singing competitions when they aren't really singers," he said.
The US version of the singing reality show tapped Spears and Lovato as replacements for Nicole Scherzinger and Paula Abdul. They will appear along with original judges Simon Cowell and LA Reid in its second season which will air in the fall.