A Tesla worker in a file photo from the company's Fremont, Calif., plant.
The UAW filed an unfair labor practices complaint against Tesla with the National Labor Relations Board on Wednesday after the automaker fired more than 400 employees.
The complaint alleges that Tesla Inc. discouraged organizing by intimidating employees, punishing those wearing union logos and firing workers who participated in protected activities. The filing follows a round of firings this month, leading to the departure of between 400 and 700 employees, which Tesla said was the result of performance reviews.
"Tesla, which recently fired hundreds of employees for 'performance issues,' swept up many pro-union employees in the terminations," the UAW said in a statement. "Several pro-union employees have come forward with copies of their performance reports, which show no areas of concern."
Former employees and their family members gathered at Tesla's Fremont, Calif., plant on Tuesday to protest the firings.
The electric automaker and the UAW have been openly sparring since February, when Tesla worker Jose Moran posted a blog detailing the harsh working conditions at the Fremont factory, adding that workers were in contact with the union to begin organizing. In response, Tesla CEO Elon Musk said Moran was paid by the UAW to drum up union support.
A Tesla spokesman reiterated the recent firings were a result of performance reviews, and called the UAW's complaint an "organizing tactic."
"No one at Tesla has ever or will ever have any action taken against them based on their feelings on unionization," the statement read. "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 NLRB must review the charge and determine if it is sufficient, then it will launch an investigation, which could lead to an administrative hearing and a demand for relief. The agency did not immediately respond to a request for comment.