The feisty females are the hot favourites to join the panel, with Louis Walsh and Gary Barlow thought to be the only two safe from the axe.
N-Dubz star Tulisa is widely believed to have been given her marching orders after a poor performance on last year's series - while Nicole Scherzinger's position is also in doubt, even though she's regarded as a fan favourite.
According to The Sun, show boss Cowell hasn't been in touch with the former Pussycat Dolls frontwoman - but is discussing deals with Mel and Nicole.
One of the newspaper's sources said: "It is about getting the right chemistry on each panel and the best dynamic.
"Simon’s focus is getting the American X Factor right then he’ll sort out the British show. While Louis and Gary are pretty certain to return, it is still all to play for for the women.
Another added: "Sharon is seriously back in contention, as is Mel — it could go down to the wire."
Sharon was previously a judge on the first four series of The X Factor - leaving due her infamous feud with Dannii Minogue - while Spice Girl Mel recently took her place on America's Got Talent.