The Spice Girls singer appeared in the latest series' launch episode as a guest judge, before Nicole Scherzinger signed up full time.
However, she was allegedly the first choice as the fourth permanent judge, but had commitments with the Australian version of the show, reports The Sun.
A source claimed: "Mel was our first choice. She was so quick and honest. You can't let everyone down gently or the praise is meaningless.
"There's a lot of money on the table for her next year."
Gary Barlow said that he wanted Mel B as a permanent judge back in June.
Sharon Osbourne has also spoken of her interest in rejoining the series as a judge.
The X Factor returns on Saturday, August 25 at 7.45pm on ITV1.