By Daniel Wiessner

A California federal judge has refused to dismiss a lawsuit accusing X, the social media service formerly called Twitter, of disproportionately laying off older workers when Elon Musk acquired the company last year.

U.S. District Judge Susan Illston on Tuesday said the plaintiff in the proposed class action, John Zeman, had provided enough evidence that the mass layoffs had a greater impact on older employees to continue pursing the case.

Zeman, for example, claims X laid off 60% of workers who were 50 or older and nearly three-quarters of those who were over 60, compared with 54% of employees younger than 50.

Illston ruled that the federal law banning workplace age bias allows plaintiffs to bring so-called "disparate impact" claims in a class action, an issue that has divided courts.

The judge dismissed a claim that X intentionally targeted older workers for layoffs, but gave Zeman a month to file an amended lawsuit fleshing out that claim.

Shannon Liss-Riordan, Zeman's lawyer, said "this decision validates the arguments we are making that the discrimination claims can go forward."

X did not respond to a request for comment.

The lawsuit is one of about a dozen X is facing stemming from Musk's decision to lay off about half of Twitter's workforce beginning last November.

Those cases include various claims, including that X laid off employees and contractors without the required advance notice and that Musk forced out workers with disabilities by refusing to allow remote work and calling on employees to be more "hardcore."

At least two lawsuits claim the company owes ex-employees at least $500 million in severance pay. Twitter has denied wrongdoing in those cases.

Liss-Riordan also represents about 2,000 former Twitter employees who have filed similar legal claims against the company in arbitration.

(Reporting by Daniel Wiessner in Albany, New York; Editing by Andrea Ricci)