A new video from Sen. Bernie Sanders takes a swipe at Amazon CEO Jeff Bezos, with the help of two employees who have spoken out against the company's climate policies.

The two-minute video was posted to Sanders' Senate Twitter account on Monday and features Emily Cunningham and Maren Costa, both of whom are user experience designers. In it, Cunningham and Costa discuss how they've faced retaliation from Amazon for calling out the company's climate policies. The video does not appear to be part of Sanders' presidential campaign.

Sanders video

Sanders repeated his calls for Bezos to exit the "business of fossil fuel extraction" and expressed his support for the employees' "grassroots movement."

Costa is one of at least two employees Amazon has threatened to fire for speaking out to the press. Cunningham was called into a meeting with Amazon representatives and told that she had violated the company's external communications policy for speaking to the press and posting on social media about Amazon's climate stance.

Both of them are members of Amazon Employees for Climate Justice, an advocacy group that has urged Amazon to develop a comprehensive climate change plan, among other environmental initiatives. Last April, the group published a letter that urged Amazon to transition away from fossil fuels, which was signed by more than 8,700 employees. Cunningham also presented the group's climate change proposal at Amazon's annual shareholder meeting in May 2019.

In September 2019, Bezos announced that Amazon aims to rely on renewable energy entirely by 2030 and have net zero carbon emissions by 2040. The plans were largely viewed as a response to employees' demands.

The day after Bezos' announcement, more than 1,000 employees walked out to protest Amazon's climate stance.

It was around this time that Amazon announced a change to its external communications policy. Amazon Employees for Climate Change said the updated policy "requires employees to seek prior approval to speak about Amazon in any public forum while identified as an employee."

In a statement, the group told CNBC: "Not one of us was told that we were breaking any policy until HR called us into private meetings in late October 2019."

However, Amazon has said the policy isn't new and that the company tried to streamline the process by adding a form on an internal website where employees could seek approval. Prior to that, employees had to get direct approval from a senior vice president.

Cunningham said she remains skeptical about why Amazon changed the policy.

"I think the purpose in changing the policy was to silence us was to scare us, but I know for myself and so many people at Amazon, we're more afraid of the climate crisis than we are by any kind of policy," Cunningham said. "It's that big and urgent of an issue."

Representatives from Amazon weren't immediately available for comment on the Sanders video.