Flores, who seeks unspecified damages, also charges that Brit abused her children, Sean Preston, 4, and Jayden James, 3, by performing sex acts in their presence.
Brit on Thursday denied Flores' allegations.
"This lawsuit is another unfortunate situation where someone is trying to take advantage of the Spears family and make a name for himself," she said in a statement.
Addressing the child abuse claims, Brit said that "the Department of Children and Family Services conducted a proper investigation surrounding Mr. Flores' accusations and have closed the case without further action." The department's findings have not been made public.
Brit's ex-husband, Kevin Federline, 32, who has primary custody of their two boys, has come to her defense. "He is satisfied that the allegations are a product of economic motives," his lawyer, Mark Vincent Kaplan, says. "They are as baseless as they seem."
No comment from Flores. The first hearing in his case is scheduled for Jan. 25.
LiLo Files: Media campaign
Ex-con Lindsay Lohan, 24, who continues to work on her sobriety, is poised to drum up some positive PR by telling her tragic, and no doubt telegenic, tale on a daytime gabfest.
But which media outlet will get the honor?
The New York Daily News says, like, a hundred thousand TV networks are engaged in a no-holds-barred death match to get LiLo first.
RadarOnline bets on Oprah, whose show begins its final season on Monday.
TMZ says NBC's Today is more likely to get the get of the year.
LiLo's mom, Dina, who had a chat with Today's Matt Lauer before LiLo's release, tells TMZ that no final decision has been made.
LiLo Files: A mini-LiLo?!
