Britney Spears' ex asking for more child support?Los Angeles, March 19 (AZINS) Singer Britney Spears' father Jamie Spears is reportedly upset with his daughter's former husband Kevin Federline, who called him pleading for more child support.

Federline has been pulling in $20,000 a month for child support for years, but he now says it's not enough. Sources told tmz.com that last Friday, Federline called Jamie and said he was in a financial bind and wanted to talk about raising his child support.

Jamie was suspicious and asked Federline where the $20,000 was going.

Sources said last week Jamie got a letter from Federline's lawyer, asking him if they could sit down and talk. They did indeed have a talk, and the lawyer explained now that 12-year-old Sean and 11-year-old Jayden have gotten older, Federline needed more than $20,000.

Jamie pressed again, asking what the children needed that they weren't getting. Federline's lawyer wouldn't answer, but said his client needed the means to take care of the two children at Britney's level.

Sources told tmz.com that the lawyer repeatedly talked about Britney's recent successes -- particularly her sold-out Las Vegas shows -- saying she was making a lot more money.

Jamie kept pushing back saying Britney's success has nothing to do with the needs of the children, and his daughter wasn't responsible for taking care of Federline and his other family members.

Britney has paid Federline a fortune in various forms of support over the years. When they divorced in 2007, she cut him a cheque for $1.3 million and he got spousal support for several years and continues to get child support.