EXCLUSIVE

Britney Spears' dad, Jamie, is super upset at Kevin Federline, who called him pleading for more child support when, in fact, all he wants is to jump on her gravy train.

Sources connected to Britney tell TMZ, last Friday K-Fed called Jamie and said he was in a financial bind and wanted to talk about raising his child support. TMZ broke the story K-Fed has been pulling in $20k a month for child support for years, but he now says it's not enough.

We're told Jamie was suspicious and asked Kevin where the $20k was going, but Kevin hedged.

Our sources say, last week, Jamie got a letter from Kevin's lawyer, asking him if they could sit down and talk. They did indeed have a talk, and we're told the lawyer explained now that 12-year-old Sean and 11-year-old Jayden have gotten older, Kevin needed more than $20k.

We're told Jamie pressed again, asking what the kids needed that they weren't getting. We're told Kevin's lawyer wouldn't answer, but said his client needed the means to take care of the 2 kids at Britney's level. Jamie fired back ... Britney's taking care of the kids the way she always did -- nothing's changed.

Our sources say the lawyer repeatedly talked about Britney's recent successes -- particularly her sold-out Vegas shows -- saying she was making a lot more money. We're told 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 Kevin and his other families.

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