Justin Bieber's publicity team is aggressively denying allegations that he fathered a baby with Mariah Yeater, a 20-year-old woman who claims she had sex with Bieber backstage at the Staples Center in Los Angeles after a concert one year ago.

Yeater is demanding that Beiber take a paternity test to scientifically confirm he is the father of the three-month-old , according to a lawsuit obtained by Star magazine and widely reported on by more reliable media outlets.

While we haven't yet seen the lawsuit, it's sad that someone would fabricate, malicious, defamatory and demonstrably false claims, Bieber's publicist said in a statement published by MTV.com. We will vigorously pursue all available legal remedies to defend and protect Justin against these allegations.

According to the upcoming Star magazine report, in a hand-signed affidavit, sworn under the penalty of perjury, Yeater told a California court that Bieber propositioned her on October 25 of last year, when she was 19. The pair had a sexual tryst after his concert and backstage at L.A.'s Staples Center, it's alleged in court papers.

According to the lawsuit reportedly obtained by Star magazine, Yager went into detail about how the encounter unfolded a year ago. RadarOnline published excerpts of her lawsuit:

After waiting for a short period of time with several young women, Justin Bieber appeared and engaged me in conversation.

Immediately, it was obvious that we were mutually attracted to one another, and we began to kiss. Shortly thereafter, Justin Bieber suggested that I go with him to a private place where we could be alone.

I agreed to go with him and on the walk to a private area, he told me he wanted to make love to me and this was going to be his first time... After walking away from the other people backstage, Justin Bieber found a place where we could be alone -- a bathroom.

Beiber would have been 16 at the time.

Mariah reportedly told a judge, When I later realized I was pregnant with Justin Bieber's baby, I tried to contact him through his representatives but no one ever called me back.

She added: On July 6, 2011, I gave birth to a baby boy. That was exactly 36 weeks and two days after the sexual encounter with Justin Bieber. Based upon the timing as well as the fact there were no other possible men that I had sex with that could be the father of this baby, I believe that Justin Bieber is in fact the father of my baby.

The full Star magazine report is expected to hit stands on Thursday.

Beiber appears to have been indirectly responding to the allegations in a recent post on Twitter that reads, all the rumors...the gossip....Im gonna focus on the positives....the music.