Kevin Federline subpoena's Britney Spears' rehab facility

The rehab center that troubled popstar Britney Spears attended in March this year, has been subpoenaed by her ex husband, Kevin Federline in relation to their custody battle over their two sons, Sean Preston and Jayden James.

An executive administrator from Promises rehab facility was served with a subpoena, confirms Federline's lawyer, Mark Vincent Kaplan.

Promises, the rehab facility, refused to comment saying, This is a confidential facility and we cannot comment.

Federline served Spears' former assistant & cousin Alli Sims and bodyguard with papers to testify in court over Spears' alleged lack off mothering skills.

The pair became officially divorced this month and first agreed on joint custody of the boys. Federline is now seeking primary custody, claiming Spears is not suitable to be a mother.