More than 1,000 Google employees have signed a letter protesting against the company’s secretive plan to build a search engine that would comply with Chinese censorship.

The letter’s contents were confirmed by a Google employee who helped organise it but wished to stay anonymous. It calls on executives to review the company’s ethics and transparency; says employees lack the information required “to make ethically informed decisions about our work”; and complains that most employees only found out through media reports about the project, nicknamed Dragonfly.

“We urgently need more transparency, a seat at the table and a commitment to clear and open processes: Google employees need to know what we’re building,” says the document.

According to a New York Times report, Google engineers are working on software that would block certain search terms and leave out content blacklisted by the Chinese government, so the company can re-enter the Chinese market.

Google left China eight years ago due to censorship and hacking.

On Thursday, according to the New York Times, Google’s chief executive told staff that development of the search engine was at an early stage and the company was not close to launching a search app in China. Sundar Pichai told a company-wide meeting that providing more services in the world’s most populous country fits with Google’s global mission.

Company executives have not commented publicly on Dragonfly and the remarks at the company meeting are the first time the project has been mentioned since details about it were leaked.

Employees have asked Google to create an ethics review group with rank-and-file workers, appoint ombudspeople to provide independent review and internally publish assessments of projects that raise substantial ethical questions.

Three former employees involved with Google’s past efforts in China told Reuters that current leadership might think that offering limited search results in China is better than providing no information at all.

The same rationale led Google to enter China in 2006. It left in 2010 over an escalating dispute with regulators that was capped by what security researchers identified as state-sponsored cyberattacks against Google and other large US firms.

The former employees said they doubt the Chinese government will welcome back Google. A Chinese official, who declined to be named, told Reuters this month that it was “very unlikely” Dragonfly would be available this year.

Google already offers a number of apps to Chinese users, including Google Translate and Files Go, and the company has offices in Beijing, Shenzhen and Shanghai. But the largest of its services – search, email and the Play app store – are all unavailable.

Google’s co-founder Sergey Brin has previously cited his birth in the Soviet Union in the 1970s as explaining his opposition to enabling Chinese censorship. “It touches me more than other people having been born in a country that was totalitarian and having seen that for the first few years of my life,” he told the Guardian in 2010, as Google pulled its censorship from Chinese search after four years of cooperating with the authorities.

The Chinese human rights community said Google’s acquiescence to China’s censorship would be a “dark day for internet freedom”.