Credit: Kevin Winter/NBCUniversal/Getty

He's nobody's Bieber-daddy.

According to Star magazine, Mariah Yeater claims she had sex with Justin Bieber backstage at an L.A. show. The 20-year-old says three months ago she gave birth to the 17-year-old pop star's son. But Bieber and his team are setting the record straight on Yeater's shocking lawsuit.

"It's sad that someone would fabricate malicious, defamatory AND demonstrably false claims," Bieber's rep told Us Weekly in a statement Monday. 

Bieber himself, who is promoting his newly released Christmas album Under the Mistletoe, addressed the controversy on Twitter: "So I'm going to ignore the rumors," he wrote. "And focus on what is real: an opportunity to help by doing what I love." 

"Judge me on the music!" he added. "Love y'all."

A portion of the profits from Bieber's holiday album will go to charity. "I'm trying to help give back," he tweeted. "Nothing will stop me from that focus. NOTHING."

Bieber's rep told Us the star and his team "will vigorously pursue all available legal remedies to defend and protect Justin against these allegations."