Kevin Federline claimed that his ex-wife Britney Spears’ “erratic behavior” is worse than what people see on the surface.

“I’m really worried,” the former backup dancer told “Entertainment Tonight” in an interview released on Tuesday.

“I’m absolutely — as a father — terrified that one day I might wake up and my sons are going to have to deal with the unimaginable,” he added, referring to his and the singer’s two kids: Sean Preston, 20, and Jayden James, 19 .

“I kinda have to sound the alarm that I truly feel that somehow, someway, I just wish that their mom would get help,” Federline, who was married to Spears from 2004 to 2007 , added.

The actor, 47, explained that he briefly shares his concerns about the “Toxic” songstress, 43, in his forthcoming memoir, “You Thought You Knew,

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