SAN FRANCISCO (AFP) - A gender discrimination trial launched here Tuesday pits an iconic venture capital firm against an employee shown the door not long after her affair with a married partner.

A jury is being asked, essentially, to decide whether the suit filed by 45-year-old Ellen Pao is a stand against a boys club atmosphere at Kleiner Perkins Caufield and Byers, or a money grab by an employee who lacked the skills to join the rarified ranks of Silicon Valley venture capitalists.

Pao lawsuit asks for US$16 million (S$21 million) in pay she contends she would have made if she had not been shown the door at KPCB in late 2012, six months after she filed her lawsuit.

The civil trial began Tuesday in San Francisco Superior Court after settlement talks failed.

Pao's attorney Alan Axelrod told jurors that he intended to show there was not a "level playing field" when it came to the career paths of men and women at KPCB.

Axelrod said that Pao was snubbed at a celebratory work dinner, being told that "women kill the buzz". Pao also contended she was given a book of salacious poetry by a male colleague.

Pao and another women were past over for promotion in favour of men with less tenure at KPCB, according to Axelrod.

Jurors were promised that they would hear Pao tell of being subjected to talk about porn stars and trips to the Playboy mansion while on a private jet with colleagues during a business trip.

Pao said in her suit that she and another woman on the investment team, Trae Vassallo, were asked to take notes at an off-site work event, evidently due to their gender.

Pao also protested that her performance review was left in the hands of a partner with whom she had an affair that ended angrily after she learned he did not plan to leave his wife and children for her.

Attorneys for KPCB countered that Pao was hired in 2005 to be an office manager for renowned partner John Doerr and years later got a chance at an investment role but didn't make the grade.

"The evidence will show that it wasn't because this was a woman, or because she had an affair with a co-worker, or because she complained of the affair," KPCB attorney Lynne Hermle told jurors.

"Ellen Pao did not have the necessary skills for that job; she did not come close."

KPCB was established in 1972 and became a revered Silicon Valley venture capital firm by backing successes such as Facebook, Amazon, and Google.

Hermle told jurors that Doerr has been on a mission for years to increase the number of women in venture capital and would testify at the trial.

Doerr hired Pao in a technical aide position to write speeches; do research, and other tasks.

Hermle provided a glimpse at performance reviews spanning years that indicated Pao was often at the centre of team controversy and "at some point in time, Ellen was not getting along with someone".

The performance evaluations show that members of the investment teams were all competitive, but "who is penalised for trying to be the best she can: the woman," Axelrod said.

The same married partner with whom Pao had an affair was later accused of making advances on Vassallo, who no longer works at KPCB.

After being called as the first witness in the case, Vassallo told of being invited out for drinks in 2009 by Ajit Nazre in what she thought was an outing to discuss KPCB investments in eco-friendly technologies.

"He started touching me with his leg under the table and at that point it was clear to me he was not there to talk green tech strategy," Vassallo said under questioning by Axelrod. "I quickly got up and left."

Years later, Nazre invited Vassallo to dinner during an out-of-town business trip under a pretence of meeting with an executive who never showed, according to Axelrod.

Vassallo testified that later there was a knock on her hotel room door and she opened it to see Nazre standing there in a bathrobe and slippers. He asked to come inside, she said.

A complaint to KPCB prompted an investigation that substantiated Vassallo's version of events.

Pao resisted an investigation of her complaint, opting instead to pursue the potential for KPCB to discuss the potential of a separation package of US$10 million or more, according to Hermle.

After seven years at KPCB, Pao was let go.

Pao took a position with popular news discussion bulletin board Reddit and is now interim chief executive.