An allegation that Justin Bieber fathered a baby by a woman who has filed a paternity suit is "demonstrably false", a spokeswoman for the singer said.
Melissa Victor said in a statement that Bieber's camp will "vigorously pursue all available legal remedies" in response to the allegation.
"While we haven't yet seen the lawsuit, it's sad that someone would fabricate malicious, defamatory and demonstrably false claims," Ms Victor said.
Online court records show Mariah Yeater filed a paternity lawsuit against Bieber (17) on Monday in San Diego Superior Court. California law keeps paternity matters confidential but Radar Online posted a copy of the lawsuit on its site.
Ms Yeater (20) said she had sex with Bieber after one of his concerts at the Staples Centre in October 2010, according to the posted suit.
She said she gave birth to a boy in July and believes the teen heartthrob is the father because there were no other possible men she had sex with at that time.
She is asking a judge for child support and a paternity test.
Ms Yeater "is pursuing a modest and rightful claim", lawyers Lance Rogers and Matthew Pare said.
"There is credible evidence that Justin Bieber is in fact the father of her baby."
The lawyers also claim that Bieber has not denied he had unprotected sex with Ms Yeater following the concert.
"We call upon Justin Bieber and his attorneys to reach out to resolve this issue in a reasonable manner," they said.
Bieber tweeted that he was going to ignore the rumours and he should be judged on his music.