Tesla employees have been given an ultimatum by their CEO, who asked them to return to work at the office or leave the company, according to an email that has been circulating on social media.

“Everyone at Tesla is required to spend a minimum of 40 hours in the office per week,” Elon Musk wrote in the email sent on Tuesday night and seen by Reuters.

“If you don’t show up, we will assume you have resigned.”

“The more senior you are, the more visible must be your presence,” Musk wrote. “That is why I lived in the factory so much – so that those on the line could see me working alongside them. If I had not done that, Tesla would long ago have gone bankrupt.”

Two sources confirmed the authenticity of the email reviewed by Reuters. Tesla did not respond to a request for comment.

Major tech firms in Silicon Valley do not require workers to return to the office full-time, in the face of resistance from some workers and a resurgence of coronavirus cases in California.

Tesla has moved its headquarters to Austin, Texas, but has its engineering base and one of its factories in the San Francisco Bay area.

“There are of course companies that don’t require this, but when was the last time they shipped a great new product? It’s been a while,” Musk wrote in the email.

“Tesla has and will create and actually manufacture the most exciting and meaningful products of any company on Earth. This will not happen by phoning it in.”

One of Musk’s Twitter followers posted another email that Musk apparently sent to executives asking them to work in the office for at least 40 hours per week or “depart Tesla.”

In response to this tweet, the billionaire, who has agreed to take Twitter private in a $44 billion deal, said, “They should pretend to work somewhere else.”

Some Tesla workers expressed displeasure over Musk’s latest comments in posts they placed on the anonymous app Blind, which requires users to sign up using company email as proof of employment at firms.

“If there’s a mass exodus, how would Tesla finish projects? I don’t think investors would be happy about that,” one Tesla employee wrote.

“Waiting for him to backpedal real quick,” another worker posted.

A California-based workers advocacy group assailed Musk’s return to office plan.

“Employers including the state government are finding that mandating a return of all employees is a recipe for outbreaks,” Stephen Knight, executive director at Worksafe, wrote in an emailed statement to Reuters.

“Unfortunately Tesla’s disregard for worker safety is well documented, including their flouting of the county public health department at the start of the pandemic,” he wrote.

In May 2020, Musk reopened a Tesla factory in Fremont, California, defying Alameda County’s lockdown measures to curb the spread of the coronavirus. Tesla reported 440 cases at the factory from May to December 2020, according to county data obtained by legal information site Plainsite.

Last year, Musk’s rocket company SpaceX reported 132 COVID-19 cases at its headquarters in the Los Angeles-area city of Hawthorne, according to county data.

Musk previously played down the risks of coronavirus, saying “the coronavirus panic is dumb” and children were “essentially immune” to the coronavirus. He later got COVID-19 twice.

Musk said last month, “American people are trying to avoid going to work at all,” whereas Chinese workers “won’t even leave the factory type of thing.”

“They will be burning the 3 a.m. oil,” he said at a conference.

Tesla’s Shanghai factory has been working all-out to ramp up production following the lockdown of the Chinese economic hub which forced the factory to shut for 22 days.

While some big employers have embraced voluntary work-from-home policies permanently, others, including Alphabet Inc.'s Google, are asking employees to return to the office gradually.

Alphabet has required employees be in offices at least three days a week starting in early April, but many employees have been approved for fully remote work.

Twitter CEO Parag Agrawal tweeted in March that Twitter offices would be reopening but employees could still work from home if they preferred./Reuters