The speculation reportedly began when Cowell's ex-girlfriend, model Jasmine Lennard, announced her pregnancy but refused to name the dad.
However, Contactmusic reports that Cowell's spokesperson dismissed the gossip and claimed that the X Factor judge hasn't seen Lennard for months.
"There is no point in asking [Cowell] when I know the answer," the representative said. "It is a lovely thought, but not unless it is a kind of divine conception.
"I don't think he has spoken to her for about a year."