A 20-year-old woman from California is said to have filed a lawsuit claiming that Bieber is the father of her 3-month-old daughter and has asked the singer to take a paternity test. She alleges that the pair met backstage at one of the 'Mistletoe' star's concerts in October 2010.
Bieber's spokesperson told TMZ: "While we haven't yet seen the lawsuit, it's sad that someone would fabricate malicious, defamatory, and demonstrably false claims.
"We will vigorously pursue all available legal remedies to defend and protect Justin against these allegations."
Bieber - whose new Christmas album Under the Mistletoe was released today (November 1) - performed on Dancing with the Stars alongside Boyz II Men earlier this evening.
He has also been confirmed as a performer for the forthcoming MTV European Music Awards in Belfast this Sunday (November 6), joining a bill that includes Coldplay, David Guetta, Lady GaGa and Red Hot Chili Peppers.
The ceremony will be hosted by Bieber's girlfriend Selena Gomez.
Watch the video to Justin Bieber's Christmas-themed single 'Mistletoe' below: