A group of Google employees published an open letter on Tuesday calling on their employer to cancel its plans to build a censored search engine for China, the latest expression of worker unrest at a company that earlier this month saw thousands stage walkouts over its handling of sexual misconduct cases.

Google’s plan for returning to China, which is known as Project Dragonfly and would reportedly allow the Chinese government to blacklist certain search terms and control air quality data, has garnered significant backlash internally since it was first reported on in August. More than 1,400 Google employees signed an internal petition criticizing the lack of transparency around the project, and at least one employee resigned in protest.

But Tuesday’s letter, which was signed by nine current Google employees, is a bold step for employees of a company that prizes internal transparency but considers leaking information to be not “Googley”.

“Many of us accepted employment at Google with the company’s values in mind, including its previous position on Chinese censorship and surveillance, and an understanding that Google was a company willing to place its values above its profits,” the letter reads. “After a year of disappointments … we no longer believe this is the case.”

Project Dragonfly has been roundly criticized by human rights organizations, a group of which warned that “by accommodating the Chinese authorities’ repression of dissent, Google would be actively participating” in human rights violations. The project would reportedly allow a Chinese company that partnered with Google to access users’ search history by querying their phone numbers.

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“Giving the Chinese government ready access to user data, as required by Chinese law, would make Google complicit in oppression and human rights abuses,” the Google employees wrote in their letter. “Dragonfly would also enable censorship and government-directed disinformation, and destabilize the ground truth on which popular deliberation and dissent rely …

“We refuse to build technologies that aid the powerful in oppressing the vulnerable, wherever they may be.”

The latest employee protest comes amid a growing labor movement of technology workers, one that has focused not just on working conditions, but also on ethical considerations related to the work itself. In recent months, employees at companies including Microsoft, Amazon and Salesforce have spoken out internally about their employers’ work for Immigrations and Customs Enforcement (Ice) or Customs and Border Protection (CBP) in the United States, amid an immigration crackdown by the Trump administration.

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In April, Google employees anonymously protested against the company’s work helping the US Department of Defense to deploy artificial intelligence and machine learning to analyze drone footage. And there have been mass worker protests following a report in the New York Times revealing allegations of sexual harassment and assault by a number of Google executives, one of whom reportedly received a $90m severance package.

Thousands of Google employees staged walkouts at workplaces around the globe. Google has since acceded to some of the workers’ demands – including an end to forced arbitration in cases of harassment or discrimination.