Britney Spears’ second ex-husband, Kevin Federline, is saying the quiet part out loud when it comes to her erratic behavior since being freed from her controversial conservatorship in 2021.

In his upcoming memoir, the former dancer and actor — with whom the pop icon shares two adult sons — is calling into question her mental wellness and parenting skills.

“The truth is, this situation with Britney feels like it’s racing toward something irreversible,” he writes in one of the chapters of “You Thought You Knew.”

In exclusive excerpts from the memoir shared by The New York Times on Tuesday, Federline writes: “It’s become impossible to pretend everything’s OK. From where I sit, the clock is ticking, and we’re getting close to the 11th hour.”

“Something bad is going to happen if things don’t change,” he continues, “and my biggest fear is that our sons will be left holding the pieces.”

The former couple tied the knot in 2004 and finalized their divorce in 2007 — the same year that Spears infamously shaved her head and attacked a paparazzo with an umbrella. Months later, she was placed on a 5150 involuntary psychiatric hold and later into a “temporary” conservatorship that ultimately lasted nearly 14 years.

At the time, Federline had already been granted primary physical custody of their two sons: Sean Preston, now 20, and Jayden James, 19.

In a damning allegation made in the book, Federline claims that Spears’ disturbing behavior continued for years, and that their sons, as teenagers, expressed fear over visits with their mom.

“They would awaken sometimes at night to find her standing silently in the doorway, watching them sleep — ‘Oh, you’re awake?’ — with a knife in her hand. Then she’d turn around and pad off without explanation,” he writes.

Ever since the 43-year-old “Toxic” singer’s conservatorship was terminated, she has continued to exhibit what some have viewed as concerning behavior on social media. Included in those posts are countless videos of her dancing and singing in the nude — and sometimes wielding knives.

Federline writes in his book that he feels the “Free Britney” movement — launched by a legion of fans who advocated for the court-ordered conservatorship to be lifted — “started from a good place” but turned out for the worst.

“All those people who put so much effort into that should now put the same energy into the ‘Save Britney’ movement. Because this is no longer about freedom. It’s about survival,” he writes. “Now, more than ever, [our children] need your support. I’ve been their buffer for years, but now it’s bigger than me. It’s time to sound the alarm.”

In a statement to Billboard, a representative for Spears dismissed Federline’s claims, accusing him of merely trying to make a profit.

“Sadly [the book] comes after child support has ended with Kevin,” the rep said. “All she cares about are her kids … and their well-being during this sensationalism.”

“You Thought You Knew” is set to be released on Oct. 21.

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