Murphy, who stars in the upcoming "Dreamgirls" film, was recently asked if he was excited that Brown -- known as Scary Spice when she was in the megahit group of the '90s -- was pregnant. She has been photographed recently with an expanding belly.
"So are you happy with her because she's pregnant with your child?" asks the TV interviewer, apparently referring to Brown.
"Now you're being presumptuous because we're not together anymore," Murphy replies. "And I don't know whose child that is until it comes out and has a blood test. You shouldn't jump to conclusions, sir."
A clip of the interview was posted Tuesday on the TMZ.com Web site.
Arnold Robinson, a spokesman for Murphy, told The Associated Press he doesn't comment on Murphy's personal life.
The AP was attempting Tuesday to find a representative for Brown.
Murphy, 45, escorted film producer Tracey Edmonds to the premiere of "Dreamgirls" in New York on Monday night. When asked by AP Television News if Edmonds is his "new lady," he smiled and replied, "Yeah."
People magazine, on its Web site Tuesday, quoted Edmonds, the ex-wife of singer Kenneth "Babyface" Edmonds, as saying she's been dating Murphy "for about a month and a half."
Murphy's wife, Nicole, filed for divorce last year, citing irreconcilable differences. The couple were married in 1993 and have five children together.