03/10/2008 at 08:00 AM EDT
's father, Jamie Spears, is expected to join attorneys appearing before a Los Angeles family law judge on Monday, to complain that the lawyer for her ex, Kevin Federline
, has overcharged the pop star.
Sources say Britney's new custody attorney, Stacy Phillips, will dispute a $500,000 tab from K-Fed attorney Mark Vincent Kaplan, as well as a $600,000 bill from Britney's previous custody attorney, Sorrell Trope.
The main agenda item, however, will be the invoice from Kaplan, who, according to sources, was deposed on the matter last week, as was Kaplan's former spokesman.
Elliot Mintz, a new spokesman for Kaplan, declined to comment until after Monday's hearing before Los Angeles Superior Court Commissioner Scott Gordon.
In the afternoon, attorneys representing Jamie Spears, who is also serving as temporary co-conservator
for his troubled daughter, will appear before a probate court commissioner to discuss a timetable for updates on her psychiatric condition.
Last week, the commissioner extended
the temporary co-conservatorship until July 31, but sources say Britney could regain control of her finances sooner should she continue to respond well to treatment.