"At the end of the day, he's coasting," Sir Elton tells Rolling Stone in its new cover story. "I always say, 'Billy, can't you write another song?' It's either fear or laziness. It upsets me."
The musician clearly takes Joel's problem seriously – and personally. "Billy's a conundrum," John, 63, says of the 61-year-old. "We've had so many canceled tours because of illnesses and various other things, alcoholism."
Addressing Joel's drinking, John says: "He's going to hate me for this, but every time he goes to rehab they've been light. When I went to rehab, I had to clean the floors. He goes to rehab where they have TVs."
Directing his comments to the Piano Man, the Rocket Man says: "I love you, Billy, and this is tough love. Billy, you have your demons and you're not going to get rid of them at rehab light. You've got to be serious. People adore you, they love you and respect you. You should be able to do something better than what you're doing now."
In response to John's remarks, Joel issued a statement. It said, "I've worked with Elton for such a long time and I've enjoyed our relationship too much to let something as random as these comments change my affection for him. Elton is just being Elton."
With additional reporting by JOEY BARTOLOMEO