The Hollywood star was alleged to be the favourite to land a part as a feisty businesswoman rivalling Kim Cattrall's maneating character Samantha Jones in a follow-up to the 2008 box office smash.
An insider told Britain's The Sun newspaper, "The character they want her to play is a really ballsy, high-powered company executive who tangles with Samantha.
But Holmes' representatives are baffled by the reports, insisting there is "no truth" to the claims, according to GossipCop.com.
The Sex and the City movie sequel is expected to begin shooting in late August (09)/early September (09).