In a letter to the Senate Committee on Commerce, Science and Transportation, former Google research scientist Jack Poulson details why he stepped down from the company in late August. The note, sent earlier this week, details growing concern over Project Dragonfly, the search giant’s attempt to enter the Chinese market in a meaningful way.

The letter arrived as the Senate prepared to question Google’s new chief privacy officer, Keith Enright, about data concerns. It seems likely that the subject of Dragonfly will be on the schedule for committee members. Nearly 1,400 employees signed a letter last month stating that the project, “raise[s] urgent moral and ethical issues.”

“It is notable that Project Dragonﬂy was well underway at the time the company released its AI Principles,” Poulson writes in his own letter. “As has been widely understood, by human rights organizations, investigative reporters, Google employees, and the public, Project Dragonﬂy directly contradicts the AI Principles’ commitment to not ‘design or deploy’ any technology whose purpose ‘contravenes widely accepted principles of […] human rights.’ ”

Poulson highlights four specific issues that have caused concern internally at the company. The list includes tying search queries to phone numbers and a blacklist of search terms including “human rights,” “student protest” and “Nobel Prize,” developed in conjunction with the Chinese government. The former employee also highlights government control over air quality data and the “catastrophic failure of the internal privacy review process.”

Yesterday, reports surfaced that CEO Sundar Pichai will meet with Republican lawmakers to discuss Google’s China plans and GOP concerns over search bias.