Amazon has warned two employees who publicly criticized the tech giant's environmental policies that they could be fired in the future for violating its communications policy, according to a Thursday report.

The Washington Post, which is owned by Amazon CEO Jeff Bezos, writes that a lawyer for the retail behemoth's employee-relations group sent a letter to two workers who were quoted in an October report in the newspaper, accusing them of being in violation of the company's external communications policy.

In an email sent to Maren Costa, the Post reports, a principal user-experience designer at the company, Amazon warned that future infractions could “result in formal corrective action, up to and including termination of your employment with Amazon.”

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Protestors unfurled anti-Amazon banners from the balcony of a hearing room during a New York City Council Finance Committee hearing at New York City Hall, January 30, 2019.  (Photo by Drew Angerer/Getty Images)

Protestors unfurled anti-Amazon banners from the balcony of a hearing room during a New York City Council Finance Committee hearing at New York City Hall, January 30, 2019.  (Photo by Drew Angerer/Getty Images)

Costa was advised by the lawyer in the human resources group to "review the policy again" anytime the employee might consider speaking publicly about the Seattle company.

According to the Post, Costa and another employee told the publication in October that Bezos' company is contributing to climate change as its cloud computing business furthers the interests of oil and gas companies. Costa also reportedly met with Amazon’s human resources department to discuss the matter in October.

“It was scary to be called into a meeting like that, and then to be given a follow-up email saying that if I continued to speak up, I could be fired,” Costa told the Post via email, referring to Amazon’s warnings to her. “But I spoke up because I’m terrified by the harm the climate crisis is already causing, and I fear for my children’s future.”

“It’s our moral responsibility to speak up — regardless of Amazon’s attempt to censor us — especially when climate poses such an unprecedented threat to humanity,” Costa added.

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Amazon’s external communications policy “is not new and we believe is similar to other large companies,” company spokeswoman Jaci Anderson said in a statement to the Post. In response to a question about whether the company was trying to stifle workers, Anderson said employees are “encouraged to work within their teams,” including by “suggesting improvements to how we operate through those internal channels.”

The incident is the latest in a wave of worker activism that began over a year ago when 20,000 Google employees walked off the job to protest that company's handling of sexual harassment complaints as well as wage disparities. Workers at Amazon and Microsoft have staged a range of protests and circulated petitions against the use of facial recognition by law enforcement and government agencies.