A day after workers launched a campaign to create a union, Tesla (NASDAQ:TSLA) Inc. fired hundreds of workers from its Autopilot department at its Buffalo facility in New York on Wednesday, according to a complaint submitted to a government agency.

Tesla employees in New York said earlier this week that they will unionise with Workers United Upstate New York, which would help give them a voice at work.

In a document submitted to the US National Labor Relations Board (NLRB) on Wednesday, the Workers United Upstate New York union said that the most valuable automaker in the world had responded by firing some of the workers “in reprisal for union action.”

The corporation fired over 30 employees, according to the union, who also claimed that they were sent an email with an amended policy prohibiting workplace meetings from being recorded without the consent of all attendees.

“This policy violates federal labor law and flouts New York’s one-party consent law to record conversations.”

The workers had urged Tesla to abide by their right to unionise and urged the business to sign the Fair Election Principles, which would have prevented Tesla from intimidating or retaliating against the workers.

Elon Musk, the chief executive, has previously been outspoken about his hostility to unions and claimed in a 2018 tweet that workers would forfeit their stock options if they organised a union, which led the NLRB to request that he remove the remark.