The American Civil Liberties Union (ACLU) published an open letter addressing Amazon investors ahead of the company's shareholders' meeting on Wednesday.

The letter urges shareholders to vote on two proposals: the first blocking the sale of Amazon's facial recognition software to government agencies, and the second calling for an independent review of the civil rights impacts of the technology.

The ACLU has been vocal in its criticism of Amazon's facial recognition, along with AI experts who say the technology is more inaccurate when analyzing the faces of women and people of color.

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The American Civil Liberties Union (ACLU) called on Amazon shareholders to oppose the company's sale of its facial recognition software to government agencies in an open letter published Monday.

"Amazon has shown it will not voluntarily act to prevent the deployment of this dangerous technology, posing a material risk to the company's business reputation and the public's trust. This product threatens the safety and civil rights of people everywhere," wrote the ACLU.

The letter calls on Amazon investors to vote on two proposals coming up at the company's shareholder meeting on Wednesday. The first is a proposal to block Amazon from selling the software (called Rekognition) to the government, and the second mandating an independent review of the civil rights impacts of facial surveillance.

Read more: A US police force is running suspect sketches through Amazon's facial recognition tech and it could lead to wrongful arrests

"Amazon has shown it will not voluntarily act to prevent the deployment of this dangerous technology, posing a material risk to the company's business reputation and the public's trust. This product threatens the safety and civil rights of people everywhere," the ACLU wrote.

Rekognition has come under heavy fire in the past from the ACLU. Last year the ACLU tested the technology on members of Congress, 28 of whom it mistakenly identified as people who have previously been arrested. A group of AI experts also published an open letter in April, warning that the technology is particularly inaccurate when analysing the faces of women and people of color.

Amazon responded that the ACLU had not applied the correct "confidence threshold" which it says is necessary to use the technology. However, reports from Gizmodo and The Washington Post revealed that police in Washington County, who are currently deploying Rekognition, do not necessarily pay attention to the confidence threshold.

Inaccuracy isn't the ACLU's only concern. "Regardless of its accuracy, putting this technology in government hands creates an unacceptable risk of exacerbating racial disparities in arrests, imprisonment, and even police use of force." it wrote.