Kevin Federline Says Drunk Call From Britney, Paris, Lindsay 'Final Straw' in Marriage

Kevin Federline claims his ex-wife, Britney Spears, had a reckless pattern of prioritizing partying over their kids ... and his tell-all memoir details the moment he said enough is enough.

In his newly released book, "You Thought You Knew," Kevin writes, "I was in Miami for work, trying to stay focused on my commitments, and I got a call. It was her, Paris Hilton, and Lindsay Lohan on the line, drunk as hell, begging me to come over. I could hear Preston and Jayden crying in the background. It had to be three or four in the morning. That call was the final straw."

According to K-Fed, it wasn't the first time something like that happened, but it was the one that stuck with him the most.

"I'd already seen the photos in the tabloids, the ones of her out with them all night, partying at Paris's Malibu place," he says. "But hearing my kids crying while she was doing God-knows-what? That was it. Any deep-seated sliver of hope that I'd held onto, that we might still somehow pull it together for the kids, died right then."

Kevin remembered feeling like Britney "wasn't ready to change" and he "couldn't keep waiting for her to figure it out."

The estranged couple, who wed in October 2004 before calling it quits two years later, share two sons together -- Sean Preston and Jayden James.

As we previously reported, Kevin also alleges in the book the pop icon drank alcohol while pregnant ... among other things.