Britney Spears conservatory is angry over the hefty bills from Mark Vincent Kaplan for her ex-hubby Kevin Federline's representation. Why are Britney's peeps pissed? They want Spears to pay the bills.

Evidently Kaplan sent Federline a bill for a half million bucks for the work he has performed over the past five months.

Brit's attorney, Stacy Phillips, also held a deposition where she questioned both Kaplan and Federline about the attorney bills.

As TMZ points out, Britney is paying an attorney to contest K-Fed's lawyer. Looks like Spears is "damned if she does, and damned if she doesn't."