The 32-year-old Welsh opera singer took to Twitter to refute online allegations that she had hooked up with the L.A. Galaxy star.
"Dear Twitter friends, I've read some horrible rumors on here & want u 2 know I absolutely deny I've had an affair with David Beckham," she wrote.
"The rumors are hurtful, untrue & my lawyers tell me actionable. I've only met David twice: once at the Military Awards in 2010 & on a night out in the West End in Feb 2012.
"We were out in a group of friends & it was just a normal fun evening out.
"Just so we are clear I have never been on my own with him and never arranged to meet up."
A source told MailOnline that Victoria is "bemused by the whole thing."
"Victoria understands why Katherine would want to defend herself against these allegations," the source said but added the doting mom just wants to focus on her four children; Brooklyn, 13, Romeo, 9, Cruz, 7, and 13-month-old Harper.
"Victoria and David have been through a lot and love each other," an insider told British publication Look.
"There's no way she'd let the family get dragged into a Twitter soap opera. The rumors are not true, but that doesn't stop them being hurtful."
David denied having an affair with his former PA Rebecca Loos back in 2004, saying that he does not "flirt with other women. I exist only for Victoria."
The Spice Girl-turned-fashion-designer later said that it was a "really tough time" for her marriage to David, which has now lasted 13 years.
Katherine was runner up on Season 14 of Dancing With The Stars. She has not had a significant relationship since splitting from fiancé Gethin Jones in December 2011.