Kevin Federline’s subpoena party continued over the weekend, as another key figure in Britney Spears’ recent history was served to testify in the Chaotic couple’s custody spat.

Mark Vincent Kaplan told E! Online that “an administrative executive at Promises” was subpoenaed Saturday.

A post-buzzcut Spears put in a monthlong tour of duty at the celeb-friendly rehab center earlier this year.

Promises declined to comment on the subpoena, citing the facility’s privacy policy.

The unidentified Promises recipient is the fourth to be targeted by Team Federline in the past week, joining Spears sidekick Alli Sims, bodyguard Daimon Shippen and former assistant Shannon Funk on the testimony guest list.

All are expected to be asked about Spears’ party habits, her sometimes erratic behavior and, ultimately, her parenting prowess.

Last week, a source close to Federline told E! Online that he was torn over whether to serve Spears’ parents, especially her mother.

“Lynne Spears has stopped short of criticizing Britney in public, choosing instead to support Kevin behind closed doors. But that’s become such a sore sport between Brit and her mom,” the source said.

“Britney really resents her parents for backing Kevin. And if Kevin drags them all in court, it’s going to get so ugly.”

Federline, the source said, “knows the trouble that will cause, so he’s trying to avoid it. He doesn’t want to put Britney’s parents in that position. But if he has to, if it means the difference between getting his kids or not, he’ll do whatever it takes.”

Spears, 25, and Federline, 29, officially ended their marriage July 30, signing off on a divorce settlement that included joint custody of their sons, 23-month-old Sean Preston and 11-month old Jayden James.

However, days later, Federline dispatched Kaplan back to court to file papers seeking primary physical custody of the boys.

Federline believes that his former missus has not been a model mommy. At a court hearing last week, Kaplan said the the boys are more “isolated from risks” when they’re with Federline than when they’re with their mother.

“This has nothing to do with money,” the attorney added. “It never has.”

Spears had custody of the kids this weekend; while his minions spread the subpoena love this weekend, Federline was spotted in Las Vegas, partying with about two dozen pals at the Tao nightclub both Friday and Saturday.

Credit: E! Online