Anyone who wants to call Christina Aguilera fat will have to answer to Adam Levine.

Levine says he and Aguilera have a brother-sister relationship (Photo Credit - Pinterest)

At a press conference in New York on Friday in response to Aguilera’s haters who have criticized everything from her weight to her hair, Levine told reporters, “People shouldn’t say those kind of things, because, f—k you! Come on guys, grow up! It’s not cool. I’ve never liked it. I think it’s horrible and I’ll totally defend her when people say things like that because it’s no one’s business.”

The Maroon 5 frontman and the “Beautiful” singer have famously bickered on “The Voice,” a singing competition in which both are mentor-judges (though Aguilera recently left the show).

However, Levine, 33, insists that the on-screen tension was “never serious.”

"The fights that everyone thought we were having were fictional," he tells People magazine, "We never hated each other. We never had these secret battles that everyone thought we were having. They were silly bickering things that brother and sister would do, it’s not nearly what everybody thought. We’re all good, Christina and I.”
 
Just like an older brother would, Levine dislikes it when people bash on Aguilera, 31. “It pisses me off, and of course I have her back, of course I defend her. It’s not nice to just have your bread and butter and be trashing other people. That’s bullying.”
 
He continued on the subject of bullying, and points out, “Everyone’s so obsessed with trying to end bullying and ‘It Gets Better’ and this whole thing. Meanwhile, on one hand they’re saying that, and then doing things like that – that’s bullying," he added.

Speaking more broadly, Levine also said he doesn’t think people should attack celebrities. “Sure, we may be confident, successful people who can take a punch, but it’s just not cool.”

On her part, Aguilera has told People that she is confident with who she is, “I embrace my body, and I embrace everything about myself. I've always been one to make it very clear, love me or hate me, take it or leave it, this is who I am."

Reach Staff Reporter Kathy Le here.