Sir Elton John has a bone to pick with pal Billy Joel.
"He's going to hate me for this, but every time he goes to rehab they've been light," the legendary singer -- who went to rehab for drug and alcohol abuse in 1990 -- tells the new issue of Rolling Stone. "When I went to rehab, I had to clean the floors. He goes to rehab where they have TVs."
But the Grammy-winner, 63, stresses that his words come from a caring place.
"I love you, Billy, and this is tough love," he tells the mag. "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."
John, who welcomed son Zachary with husband David Furnish, 48, on Christmas day, adds that he thinks Joel's problems are affecting his career.
"At the end of the day, he's coasting," says John. "I always say, 'Billy, can't you write another song?' It's either fear or laziness. It upsets me. Billy's a conundrum. We've had so many cancelled tours because of illnesses and various other things, alcoholism."
But despite John's harsh words, Joel is looking to start a feud with his longtime pal. "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," he tells UsMagazine.com. "Elton is just being Elton."
For his part, John also dishes to the mag about some of his less likely friendships with rapper Eminem -- "When David and I had our civil partnership, he sent us a present.....two diamond c--k rings," -- and Rush Limbaugh.
Says John of playing at the conservative radio talk show host's wedding, "I had dialogue with him before and he said, 'I'm not anti-gay, I want you to come, bring David.' My goal is for Rush to say, 'I support civil partnerships,' and if I rang him right now, I think he might agree. He was one of the first people to congratulate us on the baby."