Shannon Liss-Riordan on Monday filed a class-action lawsuit in federal court in Manhattan on behalf of three former IBM employees who say the tech giant discriminated against them based on their age when it fired them. Liss-Riordan, a partner at Lichten & Liss-Riordan in Boston, has represented workers against Amazon, Uber and Google and has styled her firm as the premier champion for employees left behind by powerful tech companies.

“Over the last several years, IBM has been in the process of systematically laying off older employees in order to build a younger workforce,” the former employees claim in the suit, which draws heavily on a ProPublica report published in March that said the company has fired more than 20,000 employees older than 40 in the last six years.

The lawsuit comes as IBM faces questions about its firing practices. In exhaustive detail, the ProPublica report made the case that IBM systematically broke age-discrimination rules. Meanwhile, the Equal Employment Opportunity Commission has consolidated complaints against IBM into a single, targeted investigation, according to a person familiar with it. A spokeswoman for the EEOC declined to comment.

In the last decade, IBM has fired thousands of people in the U.S., Canada and other high-wage jurisdictions in an effort to cut costs and retool its workforce after coming late to the cloud computing and mobile tech revolutions.

“Changes in our workforce are about skills, not age,” Ed Barbini, a spokesman for IBM said in an emailed statement. “In fact, since 2010 there is no difference in the age of our U.S. workforce, but the skills profile of our employees has changed dramatically. That is why we have been and will continue investing heavily in employee skills and retraining — to make all of us successful in this new era of technology.’’

If the judge allows a class action lawsuit to proceed, it could result in a drawn-out and costly court battle, and potentially end with IBM paying hundreds of millions of dollars to its former employees, according to Michael Willemin, an employment lawyer with Wigdor LLP who isn’t involved in any IBM-related cases.