Three women have filed a lawsuit against Google, accusing the company of discriminating against female employees by underpaying them and denying them opportunities for promotions. The plaintiffs seek to turn their complaint into a class action lawsuit covering all women who worked at Google within the last four years.

“Google has discriminated and continues to discriminate against its female employees by systematically paying them lower compensation than Google pays to male employees performing substantially similar work under similar working conditions,” the lawsuit claims.

The women say they were placed at lower pay ranks than male co-workers

The suit was filed on behalf of three women — Kelly Ellis, Holly Pease, and Kelli Wisuri — who say they were placed into lower career tracks than their male co-workers and received lower salaries and bonuses because of it. They assert that Google’s actions violate California law, including the California Equal Pay Act, and are asking for lost wages and damages, and for Google to be forced to correct its allegedly discriminatory hiring practices.

Google denies the allegations. “In relation to this particular lawsuit, we’ll review it in detail, but we disagree with the central allegations,” Gina Scigliano, senior manager of corporate communications at Google, writes in an emailed statement. Scigliano also says that Google has “extensive systems in place to ensure that we pay fairly.”

This lawsuit is far from the first claim of gender-based pay discrimination at Google. The US Department of Labor is currently investigating the company’s hiring practices and, earlier this year, testified in court that it found “systemic compensation disparities against women pretty much across the entire workforce.” Earlier this month, The New York Times published salary data, compiled by nearly 1,200 Google employees, showing disparities in both salaries and bonuses across pay grades.

Much of the lawsuit revolves around Google’s tiered pay system. Employees on higher tiers typically receive higher salaries and bonuses. “Technical” employees also receive more pay than “non-technical” employees.

“There are statistically significant disparities adverse to women across the board.”

The three women say they were put on lower tiers than their male colleagues and limited in their opportunities to move up the ladder. Ellis says she was hired with four years of experience and placed at Level 3, where new college graduates are often placed; weeks later, the suit claims, a male colleague with the same amount of experience was hired into Level 4. Ellis also claims she was put on the less-prestigious front-end development team, despite having experience in backend development. The backend team, the suit says, is higher paid and almost exclusively men.

Wisuri has a similar story. The suit says she was hired into a Level 2 sales role, while men with similar qualifications entered at Level 3. Men were more often hired into roles that received commission, too, the suit claims.

Pease entered Google with 10 years of experience as a network engineer and oversaw a team of “technical” staff, but she wasn’t considered to be a “technical” employee herself, thus limiting her pay, according to the lawsuit. The suit claims she was denied the opportunity to transition to the “technical” classification, and after returning from medical leave, was moved out of engineering entirely.

Ellis, Wisuri, and Pease all left Google over the past three years.

Scigliano, at Google, says Google’s hiring process is designed to eliminate gender biases. “Job levels and promotions are determined through rigorous hiring and promotion committees, and must pass multiple levels of review, including checks to make sure there is no gender bias in these decisions,” she writes.

James Finberg, an attorney representing the plaintiffs, says he believes the suit will be able to win class action status and cover all women at Google over the last four years. “I think those chances are very high,” he says, “because the statistical evidence that the Department of Labor collected and The New York Times collected indicate that there are statistically significant disparities adverse to women across the board.”

Finberg says he plans to request the same pay information that Google turned over to the Department of Labor and deliver an analysis to the court.

Finberg’s law firm, Altshuler Berzon, focuses on cases dealing with “economic justice.” The suit got started, he said, after the firm put out a call for stories about discrimination inside Google. Ninety people responded, he said, including the three women listed on the suit.