Kevin Federline is heating up the escalating baby battle with Britney Spears.
“Extra” has learned Kevin has filed yet another subpoena in his effort to prove he should get full custody of the kids, this time to Promises Treatment Facility in Malibu!
Promises is the rehab center where Britney stayed for nearly a month, and Kevin wants to get Britney's rehab records.
This is the fourth subpoena that Kevin's attorney, Mark Vincent Kaplan, has issued. Those closest to Britney, including former assistant Shannon Funk, friend Alli Sims and bodyguard Daimon Shippen, have all been served.
Meanwhile, “Extra” spotted Kevin partying at Tao in Vegas, and Britney – sans wig or extensions – showing off her short, blonde hair in L.A. It's been six months since her head-shaving meltdown.