Britney Spears is being accused of having cheated on Kevin Federline with a female dancer, according to the latter’s upcoming memoir.

In “You Thought You Knew,” released on Tuesday, 47-year-old Federline — who encountered and wed the pop icon, 43, in 2004 — recounts discovering Spears “engaging intimately” with one of her female dancers during a European tour amidst their “whirlwind” love affair.

“As I passed one of the rooms, I glanced inside — and froze. There she was. Theresa was sitting on the edge of the bed. Britney stood between her legs, hands on her face, and they were passionately making out,” reveals an excerpt shared by USA Today.

The former backup dancer says the alleged encounter left him with “a sudden clarity.”

”This wasn’t what I signed up for. So I got the hell out of there,” he writes. “At that point, I cared about nothing else — I just wanted out.”

Federline narrates his attempt to catch “the first flight back to the States” when the “Oops! I Did It Again” singer returned to their room to find him packing and “began apologizing, explaining, promising it would never occur again.”

“She expressed she hadn’t understood how serious I was about us, felt overwhelmed, and it was merely a mistake,” he notes. “That instant marked a pivotal moment for both of us. It was our inaugural argument. … I believe it was the moment she perceived I wasn’t interested in the fame or the perks. I was solely there for her. … My readiness to walk away … demonstrated the genuineness of it.”

The exes, who divorced in 2007, share sons Sean Preston, 20, and Jayden James, 19, for whom Spears’ child support ended in late 2024.

In an excerpt published by The New York Times, Federline expresses concerns that he fears “something unfortunate is going to happen” to Spears due to her mental health, leaving their sons “to pick up the fragments.”

Federline’s memoir arrives almost two years following the Oct. 24, 2023, publication of Spears’ groundbreaking memoir, “The Woman in Me,” which details their turbulent marriage and her prior relationship with Justin Timberlake. As of August 2024, “Wicked” director and producer Jon M. Chu and Marc Platt are slated to direct and produce a film adaptation based on the bestseller.