Britney Spears has been ordered to pay $120,000 immediately for ex-husband Kevin Federline's legal bills pertaining to their custody battle.

In making the ruling, L.A. Superior Court Commissioner Scott Gordon noted the "disparity between the parties income" and that "the vast majority of the ... litigation deals with [Spears's] conduct."

On Oct. 10, Federline's lawyer originally requested $160,000 for fees.

California law states that either party has access to legal representation to preserve their rights, even if that means one person must pay for other's attorney.

"We've already incurred more fees above the $164,000 in the document, and we expect we will be incurring significant other fees going into the trial," Federline's lawyer, Mark Vincent Kaplan, tells PEOPLE. "I intend to make further fee orders up to the date of the trial."

CelebTV.com first reported the story.

Last week it was revealed that Federline grossed $7,436 in 2006 after business expenses. Spears, however, earns approximately $737,000 per month.

The two are embroiled in a custody battle over sons Preston, 2, and Jayden James, 1.