Earlier today, a Tesla employee wrote a post on Medium alleging that he and fellow Tesla employees at the company’s Fremont, California manufacturing facility endure “excessive mandatory overtime,” lower-than-average pay, and frequent injuries. Tesla CEO Elon Musk responded to the claims in a series of private Twitter messages to Gizmodo by calling the employee, who wrote under the name Jose Moran, a pro-union agitator working on behalf of the United Automobile, Aerospace and Agricultural Implement Workers of America (UAW).

“Our understanding is that this guy was paid by the UAW to join Tesla and agitate for a union,” Musk says. The Tesla chief goes on to call Moran an employee of UAW, working on behalf of the union and not Tesla. When asked about his stance on unions, Musk describes Tesla as a “union neutral” company.

Musk suggests the Tesla employee is a pro-union agitator

In his post, Moran calls for Tesla workers to unionize to protect themselves from further mistreatment, but he says retaliation over new confidentiality policies is stoking fear among employees. “Tesla isn’t a startup anymore. It’s here to stay. Workers are ready to help make the company more successful and a better place to work,” Moran writes. “Just as CEO Elon Musk is a respected champion for green energy and innovation, I hope he can also become a champion for his employees.”

Musk tells Gizmodo that mandatory overtime, while definitely a staple of the auto industry, is decreasing each week at Tesla. He also stresses that Tesla pays higher starting wages than workers who are part of UAW. “Frankly, I find this attack to be morally outrageous,” Musk says. “Tesla is the last car company left in California, because costs are so high. The UAW killed NUMMI and abandoned the workers at our Fremont plant in 2010. They have no leg to stand on.”

Interestingly, Gizmodo points out that there are no records of anyone by the name of Jose Moran working at Tesla, either on social media or on LinkedIn, perhaps suggesting that it is a pseudonym. Although Musk’s defense of Tesla does suggest the employee’s allegations have hit upon some contentious, if not true, struggles within the company’s manufacturing ranks.

A Tesla spokesperson emailed this statement to The Verge: