Broadway "Beast" James Barbour laid his furry mitts on yet a second underage aspiring actress - this one only 13 years old - prosecutors now charge.

Barbour, a star of musical theater who once played the Beast in "Beauty and the Beast," was in Manhattan Supreme Court yesterday to answer charges that five years ago he seduced a star-struck 15-year-old actress wannabe in his Broadway dressing room.

No sooner had Barbour delivered his line, "Not guilty," than prosecutors upstaged him with their bombshell about a previous alleged victim - an even younger girl who had also come to Barbour with her starry-eyed hopes for a career in theater.

The 13-year-old contacted authorities only after reading in The Post about the alleged attack on the 15-year-old, sources said.

The younger girl's alleged seduction took place in California seven years ago - too long ago to prosecute. But Manhattan Assistant District Attorney Maxine Rosenthal told the judge that if Barbour is convicted in the case of the 15-year-old, she'll seek to have that girl's uncharged allegations count against Barbour upon his sentencing.

The 15-year-old is now a 20-year-old woman with a career in the theater. Prosecutors said she came forward earlier this year - just before the alleged contact would have become unprosecutable under the five-year statute of limitations - out of concern that there were indeed other victims.

The older alleged victim told authorities she was introduced to Barbour - a graduate of her New Jersey high school who is 20 years her senior - through the school's drama teacher.

She accuses him of seducing her into a sexual groping session back in June 2001 in his dressing room at the Brooks Atkinson Theatre on West 47th Street after his performance as Rochester in the Tony-award-winning, commercial flop "Jane Eyre."

Later that night - as the girl, her parents, and Barbour's own girlfriend dined at an Eighth Avenue restaurant - Barbour allegedly fondled her under the table. A month later, he invited her back to the city, and they exchanged oral sex at his West 98th Street apartment, she told cops.

Barbour is denying that he ever did anything more than kiss the girl. In fact, he claims he was "mentoring" her.

"At the time, I was meeting a lot of high school and college students and acting as a mentor for them in the entertainment profession," he told cops in a handwritten statement released yesterday.

It was the girl who was the aggressor, he told cops when he was arrested in his native Los Angeles back in April.

"She talked about [oral sex]," he said of their brief time together on his bed in his Upper West Side apartment.

"When the girl suggested 'sexual intercourse,' I sort of freaked out, said she was 16 and that I couldn't do this.

"The relationship stopped suddenly because I thought it was inappropriate and could get dangerous," he told cops.

Yesterday, his face visibly paled when the prosecutor told the judge that she wants the Beast caged and will seek jail time.

"It is a strong case," Rosenthal said, noting that, earlier this year, the older alleged victim caught Barbour on tape making "admissions" and admitting repeatedly that his behavior was "unethical."

The handsome Barbour came to court wearing a well-tailored gray suit, open-necked dress shirt, a wedding band on his ring finger and an attractive brunette - also sporting a wedding ring - on his arm. The couple declined to speak to reporters.

Barbour is due back in court Dec. 20.