The United Auto Workers union on Wednesday filed an unfair labor practice claim against Tesla, claiming the company harassed, intimidated, and fired workers who openly advocated for unionizing its California factory.

The claim was filed with the National Labor Relations Board, an independent government agency that seeks to enforce U.S. labor laws. This month, Tesla fired several hundred employees, citing “performance” issues.

The UAW’s complaint comes a day that a recently-fired Tesla employee has sued the automaker, claiming it violated California labor laws by failing to give proper notice when it allegedly laid off hundreds of workers this month. (Tesla said it’s confident the WARN Act, the law in question, doesn’t apply to the current situation and asserted these were firings, not layoffs, that happened over performance.)

The UAW’s complaint adds another layer of questions to the round of firings, by alleging that Tesla used a round of layoffs to dismiss workers who openly supported organizing the automaker’s factory, located in the city of Fremont.

“I was fired for trying to better the lives of my co-workers,” said Richard Ortiz, a pro-union worker who advocated for months to organize the plant, in a statement from UAW organizers. “I always felt this was a worthy fight. I knew it wouldn’t make me popular with management, and I knew there was risk – but people are getting hurt. People are being paid less than they’re worth. And people are being treated unfairly.

Pro-union Tesla workers raised the specter of being fired for supporting an organization effort in . The story quoted workers who said they received excellent marks in their most recent performance reviews. Capital & Main also found “a number of job fair listings ... throughout the Bay Area [that] suggest that Tesla will be replacing pro-union voices with contract labor.”

Along with Ortiz, the UAW says “several pro-union employees have come forward with copies of their performance reports, which show no areas of concern.”

In a statement, a Tesla spokesperson said the automaker strives to be a “fair and just company, the only kind worth being.”

“Performance reviews result in promotions and occasionally in employee departures,” the spokesperson said. “No one at Tesla has ever or will ever have any action taken against them based on their feelings on unionization. It’s worth remembering that each year, roughly 20,000 ULPs are filed with the NLRB by unions like the UAW as an organizing tactic.”

The UAW has been vocal about wanting to organize the Fremont plant since earlier this year, when Tesla employees on job pay and work conditions.

The NLRB has also filed a complaint of its own against Tesla, claiming it has found merit in employee claims that Tesla is interfering with union activities at the Fremont plant and has violated workers’ rights by requiring them to sign a broad confidentiality agreement. Tesla has said the allegations are baseless.

“I’ve worked in auto manufacturing my whole life,” Ortiz said in his statement. “I do not believe—not for a second—that I was fired for cause.”

You can read the UAW’s complaint below.