The Real Housewives of Atlanta star was responding to accusations made by Wendy Williams on her Wendy Williams Show talk show late last week.
Williams alleged that Leakes is currently separated from her husband Greg and is now dating Grant.
"NeNe allegedly has a new boyfriend -- who's on Reggie Bush's team, the New Orleans Saints -- by the name of Charles Grant," said Williams, which brought gasps from her studio audience.
"Charles has been in trouble with the law. He's been indicted on involuntary manslaughter charges."
The charge stems from a February 2008 incident outside a Blakely, GA nightclub, which resulted in the death of 23-year-old Korynda Reed -- who was pregnant at the time, RadarOnline reported Monday.
Grant's trial is scheduled to start May 3, according to RadarOnline, which added he maintains his innocence.
Rumors that Leakes may be dating Grant had first surfaced when fellow The Real Housewives of Atlanta star Kim Zolciak called into an August 2009 broadcast of Bravo's Watch What Happens: Live and alleged the relationship.
Leakes denied the accusations then and did so again when they resurfaced on Williams' show.
"Sorry girlfriend! Ur investigation is WRONG!" wrote Leakes on her Twitter account. "I'm a very smart girl & my happiness is everything 2 me."
Despite Leakes' denial, a source close to her told RadarOnline that she is "involved" with Grant.
"NeNe and Charles met at a fundraiser for him and they have been involved for over a year and a half now," the source told RadarOnline.
"Greg really loves NeNe and he wants to save the marriage but they have a lot of problems right now."
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