Kevin Federline's lawyer wants Britney Spears to pay her ex "at least three times the amount" of child support she currently gives him.
The star's celebrity divorce attorney Mark Vincent Kaplan has insisted the 'Piece of Me' singer's own representatives having not responded with "reasonable" conditions.
Speaking to Us Weekly, he claimed: "We gave them ample time and opportunity to settle Kevin's child support modification increase, and they came back with conditions that are not reasonable.
"It's their position that they don't have to turn over Britney's financial information, including tax returns, which is required under the California family code.
"It's not California celebrity code edition, she has to comply... This is the choice they have made, and they will now have to deal with it. We are still open to try and settling this without judicial intervention."
Kevin - who has 12-year-old Sean Preston and 11-year-old Jayden James with his former wife - claims he is "simply less of a 'name' and less in demand than he was in 2008" when the child support was agreed on, according to court documents obtained by The Blast.
Kaplan added: "A court hearing will be set, and the parties will engage in financial discovery, which will enable guideline support payment that Kevin should receive.
"This won't be difficult for us, Kevin is asking for the reasonable needs of the children to be met, which is at least three times the amount Kevin is currently getting.
"This is based on her earnings which have been publicly reported. We are also asking for attorney's fees because it didn't have to come to this."
Kevin - who was married to Britney for four years until 2007, and also has 15-year-old Kori and 13-year-old Kaleb with ex-fiancée Shar Jackson, and 6-year-old Jordan and 3-year-old Peyton with wife Victoria Prince - currently receives $20,000 a month from the star.