Updated 3:40 p.m. ET

Sharon Bialek alleged at a news conference today that Herman Cain reached under her skirt in 1997 as she sought help in finding a job.

The Chicago-area mother, described by her lawyer as a registered Republican, urged the GOP presidential candidate to "come clean" and admit how he was "inappropriate" with her and other women.

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Bialek's story was immediately denied by the Cain campaign, which sent out a news release as the woman spoke publicly at a New York City news conference with her lawyer, noted defense attorney Gloria Allred, by her side.

The stories of three other women have been reported by Politico and the Associated Press.

"All allegations of harassment against Mr. Cain are completely false," the Cain campaign statement said. "Mr. Cain has never harassed anyone."

The disclosure by Bialek brought a shocking twist to the allegations of sexual misconduct by Cain, which date back to his time as head of the National Restaurant Association from 1996-1999.

Cain's campaign has been roiled for more than a week by the allegations. He is tied with Mitt Romney for the GOP presidential nomination in a new USA TODAY/Gallup Poll. But 53% of Republicans say they wouldn't vote for a candidate if accusations of sexual harassment by a candidate were proven.

At the news conference, Bialek described how she went to Cain for job advice after she was let go by an educational foundation tied to the National Restaurant Association. The trade group confirms in an e-mail to USA TODAY that Bialek was employed by the National Restaurant Association Educational Foundation from Dec. 30, 1996, to June 20, 1997.

Bialek described an incident in July 1997 where she and Cain were in a car and he offered to show her the trade group's headquarters. She had reached out to Cain at the behest of her boyfriend and came to Washington as part of the job search. She was surprised to find she had been upgraded at her hotel to a "palatial suite."

Cain took credit for that upgrade, she said.

"Instead of going into the offices, he suddenly reached over and … put his hand on my leg, under my skirt toward my genitals," Bialek said about the incident in the car.

"He also pushed my head toward his crotch," she said.

Bialek described how she recently saw Cain at an event and asked if he remembered her.

"I want you, Mr. Cain, to come clean. Just admit what you did," she said. "Admit you were inappropriate to people ... and then move forward."

"Mr. Cain, I implore you," Bialek said. "Make this right. "

Allred, a longtime California attorney specializing in discrimination cases, is noted for her representation of high-profile clients. Among them: a former girlfriend of Tiger Woods, a former housekeeper for GOP gubernatorial candidate Meg Whitman, and the families of Nicole Brown Simpson and Ronald Goldman.

Allred said Bialek understands she'll face public scrutiny and chose not to sell her story. "I, for one, am disgusted at Mr. Cain's serial sexual harassment of women," Allred said, adding that the candidate is "actively lying to Americans."

As she introduced Bialek, Allred explained how her client sought advice and Cain instead provided her with "his idea of a stimulus package."

The full statement from Herman Cain's campaign: