The Wall Street bank Goldman Sachs has been hit with a sexual discrimination lawsuit from three former female employees who claim the firm has a testosterone-driven culture of press-up contests on the trading floor, male-dominated golf outings and scantily clad escorts at an office Christmas party.

Filed in New York's federal court today, the suit alleges that Goldman's decentralised structure gives broad discretion to managers in assigning pay, responsibility and advancement to employees.

"Goldman Sachs gives its managers, the overwhelming majority of whom are men, unchecked discretion to assign responsibilities, accounts and projects to their subordinates," says the complaint.

"The end result is that managers, whether based on conscious or unexamined bias, most often assign the most lucrative and promising opportunities, and 'seats', to men."

The plaintiffs are Cristina Chen-Oster, a former vice-president in bond sales who worked for Goldman for eight years until 2005; Lisa Parisi, who was in asset management from 2001 to 2008; and Shanna Orlich, an analyst from 2007 to 2008 who alleges she was denied opportunities to become a trader.

Their law firm, an aggressive specialist in class actions, which is also suing BP over its oil spill and Toyota over sticking accelerators, has set up a Goldman-targeted website and is urging other former employees to come forward.

The suit points out that the representation of women gets worse higher up the ranks at Goldman – 29% of its vice-presidents in 2009 were female but women made up only 17% of managing directors, 14% of partners and just four members of a 30-person top management committee.

The latest legal skirmish comes at an awkward time for Goldman, which recently paid $550m (£352m) to settle fraud charges brought by the securities and exchange commission. The bank is the subject of a congressional investigation over alleged unethical conduct in mis-marketing mortgage securities in the run-up to the credit crunch and is struggling to improve its public image.

Allegations in the lawsuit centre on Goldman's "black box" compensation structure, in which employees are given little explanation for variances in their pay, and the plaintiffs describe fierce competition for intangible benefits such as prime seating positions in trading rooms.

"Women at Goldman Sachs are often asked to take on responsibility for training junior employees but then penalised for diverting their attention away from generating revenues for the firm," says the complaint.

The trio make lurid allegations about specific incidents. Chen-Oster, who was paid $800,000 a year but claims her male counterparts earned twice as much, says a male colleague pinned her against a wall, "kissing and groping her" after a Goldman-sponsored staff night out at a topless bar.

Orlich claims she was excluded from golf outings, and recounts displays of "masculinity" including a push-up contest on the trading floor. And she asserts that a 2007 Christmas party for a sales team featured female escorts "wearing short black skirts, strapless tops and Santa hats".

A Goldman spokesman said: "We believe this suit is without merit. People are critical to our business, and we make extraordinary efforts to recruit, develop and retain outstanding women professionals."

Goldman insiders are likely to view the suit as an opportunistic attempt to cash in on the bank's dismal public image. The firm has been targeted by scores of recent legal assaults, including a case brought by the International Brotherhood of Electrical Workers, which complains bankers' bonuses are too high, and a stream of shareholder lawsuits over its alleged mis-selling of mortgage bonds.

Gender discrimination cases against investment banks are nothing new. In London, two former Nomura bankers lost a £3m case against the Japanese firm in April, despite claiming they were taunted by male colleagues who suggested they should be "cleaning floors".

The Equality and Human Rights Commission found last year that women working full-time in the financial sector earn 55% less, on average, than men. And the Treasury select committee has expressed concern that only 9% of board members at FTSE 100 banks are women.