Twitter is the latest Silicon Valley company to be sued over gender discrimination allegations

In the latest accusation of sexism to hit a high-profile Silicon Valley tech company, a former Twitter employee is launching a class action lawsuit against her ex-employee, Reuters reports, alleging the company's promotional system is sexually discriminatory.

Over the past several weeks, news of interim Reddit CEO Ellen Pao's lawsuit against venture capital firm Kleiner Perkins Caufield & Byers has made frequent headlines in the tech press. A judge has ruled that there's "sufficient evidence from which a reasonable juror could conclude that Kleiner Perkins engaged in intentional gender discrimination," and is now allowing Pao to pursue punitive damages.

Facebook is in the legal firing line too: Former employee Chia Hong is suing the company (using Pao's lawyers!), alleging sex discrimination, sexual harassment, and racial discrimination. Her lawyers allege she was finally fired and replaced "by a less qualified, less experienced male."

Dating app Tinder is another one. One of its female co-founders was awarded more than $1 million in damages after being forced to leave the company, saying that her coworker and ex-boyfriend Justin Mateen was verbally abusive towards her.

And an ex-Google employee claimed earlier this month that she was repeatedly sexually harassed by her superiors while working at the company, explicitly naming two senior Google employees as being complicit in the harassment. (She isn't planning to sue Google, however.)

Now, engineer Tina Huang is accusing microblogging platform Twitter of discriminating against women in the way it promotes employees internally. According to Reuters, Huang alleges the company "has no formal procedures for posting job openings or granting promotions, relying instead on a secretive 'shoulder tap' process that elevates few women to top engineering positions."

Huang, who worked for Twitter between 2009 and 2014, complained to CEO Dick Costolo and was subsequently put on leave. Court documents say that "despite being one of Twitter's oldest employees, Ms. Huang's career at Twitter was irreparably derailed for making a complaint. After three months without explanation as to the status of the investigation, or mention of any possible time frame for her return to work, she felt she had no choice but to leave the company for the sake of her career."

Mashable reports that Huang's lawyers have provided a 10-point list detailing how "Twitter's policies and practises have thus had the effect of denying equal job opportunities to qualified women":

a. Reliance upon subjective, gender-based and/or arbitrary criteria utilised by a nearly all male managerial workforce in making promotion decisions;

b. Failure to follow a uniform job posting procedure to guarantee that all employees have notice of openings;

c. Effectively discouraging women from seeking or applying for senior level and leadership positions;

d. Failing and refusing to consider women for promotion on the same basis as men are considered;

e. Failing and refusing to promote women on the same basis as men are promoted and compensated;

f. Failing to provide women with accurate and timely notice of promotional opportunities;

g. Providing women employees interested in promotion shifting, inconsistent and inaccurate statements about the requirements and qualifications necessary for promotion;

h. Establishing and maintaining arbitrary and subjective requirements for promotions which have the effect of excluding qualified women and which have not been shown to have any significant relationship to job performance or to be necessary to the safe and efficient conduct of Twitter's business;

i. Failing and refusing to take adequate steps to eliminate the effects of its past discriminatory practises; and,

j. Retaliating against women employees who complain of unequal treatment.

Twitter's workforce is overwhelmingly male, according to statistics put out by the company in 2014. Just 30% of employees are women - and in tech-related jobs, that number drops to just 10%.

Business Insider has reached out to Twitter for comment, and will update when it responds. The company provided TechCrunch with the following statement about Huang leaving the company:

Ms. Huang resigned voluntarily from Twitter, after our leadership tried to persuade her to stay. She was not fired. Twitter is deeply committed to a diverse and supportive workplace, and we believe the facts will show Ms. Huang was treated fairly.