Credit: Charles Eshelman/Getty Photo: Justin Bieber Attends the Dolce & Gabbana Boutique on Sept. 8, 2011 in New York City

According to exclusive reports from RadarOnline and Star Magazine, a 20-year-old woman named Mariah Yeater has served Justin Bieber with a paternity suit, claiming the pop star is the father of her 3-month old baby boy.

The apparent tryst happened backstage after a show in Los Angeles on Oct. 25, 2010, and according to the lawsuit, it was Justin's "first time." Mariah went into great detail about the supposed sexual encounter, telling the court that Justin refused to wear a condom, and the act itself — which she says took place in a bathroom — lasted for only 30 seconds.

Mariah is demanding a paternity test, but Justin swears the kid is not his son.

"While we haven't yet seen the lawsuit, it's sad that someone would fabricate malicious, defamatory, and demonstrably false claims," Bieber's rep told RadarOnline. "We will vigorously pursue all available legal remedies to defend and protect Justin against these allegations."

A preliminary hearing on the matter is scheduled for Dec. 15.

Source: RadarOnline