Mariah Yeater, 20, is pictured on the cover of US magazine, Star with her son, Tristyn Anthony Markhouse Yeater, born on July 6, claiming that Bieber is the father.

The 17-year-old pop superstar is now embroiled in a paternity lawsuit, filed on October 31.

Yeater has asked Bieber to support the baby, which she alleged was conceived in a tryst lasting no longer than 30 seconds.

She has demanded Bieber submit a paternity test.

In a legal statement, sworn under penalty of perjury, Yeater told a California court that Bieber propositioned her on October 25 last year, when she was 19 after his concert and at L.A.’s Staples Center.

According to US website Radar Online, Yeater 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.”

Bieber denied the allegations publicly today on his Twitter page.

He tweeted: “So Im going to ignore the rumours…and focus on what is real an opportunity to help by doing what i love. Judge me on the music! Love yall!”

Bieber’s spokesperson has vehemently denied the allegations, and told website Radar: “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.”

Yeates detailed the alleged liaison in papers submitted to a Los Angeles court.

She claims she was approached by a security guard while seated in the front row of the star’s concert and asked if she wanted to meet the singer backstage.

She said: “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.

“We went inside and immediately his personality changed drastically. He began touching me and repeatedly said he wanted to f*** the s*** out of me.

“At the time I asked him to put a condom on for protection, but he insisted that he did not want to.

“In his own words, he said that because it was his first time he wanted to feel everything.”

If Yeater was 19 and Bieber aged 16, as she claims, she would be up for statutory rape of a minor under Californian law.

A hearing date is set for December 15.

Meanwhile, The video for Justin Bieber’s Christmas single “Mistletoe” hit the web on October 18th — one of two big videos to debut that week — and it’s picked up over 28 million views since. “Mistletoe” was one of the top rising searches globally on YouTube over the past 30 days and the video has been near the top of YouTube’s music charts for the past two weeks.

Bieber is one of a few artists to have over 1 billion views, and, sometime on Sunday, Bieber’s music video channel crossed the 2 billion view threshold. “Baby” was the most-viewed music video of 2010 and still averages hundreds of thousands of views per day.