Christopher filed for a temporary restraining order against Spears on December 18 in US District Court in Tampa, Florida, claiming that 'The X Factor' judge has stolen from, blackmailed and harassed him, reported Radar online quoting The National Enquirer.
He also claimed that he fathered her son Sean Preston, 7.
"She is out-of-control and a maniac," Christopher said in the court documents.
In the papers, Christopher said Spears recently "went to Kevin's house to pick up Sean Preston and Jayden James, and (his) wallet was on Kevin's coffee table when Britney opened it up and stole (his) Capital One credit card."
Christopher claimed that when he followed up on the alleged theft, which accounted to more than USD 4,500 in charges, "Britney... laughed at me (and) told me my brother Kevin ruined her life. Britney made fun of me...
"She also blackmailed me and told me if I tell the police that she stole my credit card, that she will tell the world I'm the true father of Sean Preston, not Kevin. I do confess I slept with Britney, and I am the true father, but the public does not need to know," he said.
Spears, 31, and Kevin, 34, were married on September 18, 2004, in a nondenominational ceremony at a residence in Studio City, California after dating each other for two years.