Former American Idol contestant Clay Aiken has doubted Rihanna's singing ability.

Aiken appeared on the TV talent show in 2003 and has since launched a solo career.

Speaking on Watch What Happens, the singer was asked if there were any singers doing the rounds just now that would fail on American Idol.

However, Aiken said that there are too many - before nit-picking Rihanna's pitch. He said:

"Oh God, there are too many. Too many...Current pop singer? I've stopped listening to them because they can't sing. [I'll go with] Rihanna [because she] has some pitch problems for sure. She does...Now I'm gonna get in trouble, too."