The U.S. National Labor Relations board accused Apple of interfering with workers’ rights to collectively advocate for better working conditions by restricting their use of social media and workplace messaging app Slack, the agency said today.

The NLRB complaint, issued on Thursday, accuses the iPhone maker of maintaining unlawful work rules around the acceptable uses of Slack, illegally firing an employee who advocated for workplace changes on Slack, requiring another worker to delete a social media post, and creating the impression that employees were being surveilled via social media. This is the second time the NLRB has hit Apple with a complaint this month. Last week, the agency accused the company of requiring employees nationwide to sign illegal confidentiality, nondisclosure, and noncompete agreements and of imposing overly broad misconduct and social media policies.

Apple in a statement provided by a spokesperson today said it is committed to maintaining “a positive and inclusive workplace” and takes employee complaints seriously.

“We strongly disagree with these claims and will continue to share the facts at the hearing,” the company said.

In response to last week’s complaint, Apple denied wrongdoing and said it respects its employees’ rights to discuss wages, hours and working conditions.

If Apple does not settle with the NLRB, an administrative judge will hold an initial hearing in the case in February. The judge’s decision can be reviewed by the five-member labor board, whose rulings can be appealed in federal court.

The new case stems from a complaint filed with the NLRB nearly three years ago by Janneke Parrish, who says Apple fired her in 2021 for playing a lead role in employee activism.

Parrish used Slack and public social media outlets to advocate for permanent remote work, distribute a pay equity survey, detail alleged sex and race discrimination at Apple and post open letters critical of the company, according to the new complaint.

Slack, which allows workers to create group conversations, was rolled out several years ago at Apple and became increasingly popular as a discussion forum during the COVID-19 pandemic.

The NLRB complaint says Apple has a policy barring workers from creating new Slack channels without permission from managers. Posts about workplace concerns must be directed to a manager or a “People Support” group, according to the complaint.

Parrish’s lawyer, Laurie Burgess, said in an email today that Apple had engaged in “extensive violations” of workers’ rights.

“We look forward to holding Apple accountable at trial for implementing facially unlawful rules and terminating employees for engaging in the core protected activity of calling out gender discrimination and other civil rights violations that permeated the workplace,” Burgess said.

The complaint seeks an order requiring Apple to rescind its allegedly unlawful policies and reimburse Parrish for lost income and other financial impacts of her firing.