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Several Amazon employees say they've been threatened with termination for talking publicly about their climate change campaign.

Amazon Employees for Climate Justice, an activist group within Amazon that started in late 2018, said in a statement Thursday that four of its members were targeted by the human resources and legal departments at Amazon for speaking out publicly, including to the press. In two cases, employees received followup emails threatening firings if they continued to talk publicly, the group said.

In the group's statement, several employees called out the company for trying to quiet them.

"This is not the time to silence those who are speaking out," said Maren Costa, an Amazon user experience principal designer who says she was threatened with termination for talking to The Washington Post, which is owned by Amazon CEO Jeff Bezos.

The employee group has worked to push Amazon's leaders to make bigger commitments to reduce greenhouse gasses and cut off the company's work with the oil and gas industries. Their efforts included taking part in the Global Climate Strike in September and pushing for a failed shareholder resolution on climate change last year. Amid this work, Bezos announced a sweeping climate change plan for the company, though it didn't fulfill all the group's demands.

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Amazon Employees for Climate Justice said Thursday that its members ran afoul of a new company policy instituted in September, a day after the group announced it was organizing a climate walkout that brought out hundreds of Amazon employees at the company's Seattle headquarters. The policy requires employees to seek prior approval before talking publicly to the press or in social media about the company when they are identified as Amazon employees.

Amazon's press office responded Thursday that its external communications policy isn't new but was updated starting in the spring of last year to streamline the approvals process.

"Our policy regarding external communications is not new and we believe is similar to other large companies," an Amazon spokesperson said. "We recently updated the policy and related approval process to make it easier for employees to participate in external activities such as speeches, media interviews, and use of the company's logo. As with any company policy, employees may receive a notification from our HR team if we learn of an instance where a policy is not being followed."

The situation caught the attention of Democratic US Rep. Jared Huffman, of California, who wrote on Twitter that these threats amounted to "dismal corporate social responsibility."

The group's claims of being threatened come not long after Google faced harsh criticism for firing four employees who spoke out against working conditions at their company. The US National Labor Relations Board said last month it would investigate those terminations.

Several activist movements have cropped up at Amazon to speak out about climate change, warehouse working conditions and the company's work with immigration authorities. In many cases, employees have criticized Amazon publicly, marking a notable change for the secretive tech company. Employee movements have also come up at Microsoft, Google and other leading tech companies, showing a rise in activism in the tech industry.

CNET reviewed a copy of a November email from an Amazon human resources employee sent to Costa. In the text, the HR representative said he completed an investigation into Costa's public statements in a Washington Post article published in October and found she didn't "knowingly violate" the communications policy, so took no formal action.

"Future violations of the policy may result in formal corrective action, up to and including termination of your employment with Amazon," the email continued.

The group's statement on Thursday included quotes from five other Amazon employees, including Bobby Gordon, an Amazon finance manager who has spoken to CNET.

"Amazon's newly updated communications policy is having a chilling effect on workers who have the backbone to speak out and challenge Amazon to do better," said Victoria Liang, an Amazon software engineer. "It has nothing to do with protecting confidential data."