The lawyer representing Britney Spears in her child custody battle is suing the estate of the late Anna Nicole Smith for unpaid legal bills. Sorrel Trope claims his firm is owed $160,000 (GBP80,000) in legal fees for work carried out for Smith, who died in February (07), between October 2006 and March 2007. In a creditor's claim filed in Los Angeles Superior Court on Wednesday (07Nov07), Trope alleges the unpaid work was to do with finding out the paternity of Smith's baby daughter Dannielynn - which a DNA test proved to be Larry Birkhead. Trope is currently working for Spears as she battles her ex-husband Kevin Federline for the custody of their two sons.