In a 6,600-word internal memo to fellow workers, data scientist Sophie Zhang said she made decisions “that affected national presidents” without oversight.
“I have blood on my hands,” she wrote in the memo, parts of which were published by Buzzfeed.
In response, Facebook said it was working hard to stop bad actors and inauthentic behaviour.
In her memo, parts of which were published by Buzzfeed without her permission, Ms Zhang said: “In the three years I’ve spent at Facebook, I’ve found multiple blatant attempts by foreign national governments to abuse our platform on vast scales to mislead their own citizenry, and caused international news on multiple occasions.
“I have personally made decisions that affected national presidents without oversight, and taken action to enforce against so many prominent politicians globally that I’ve lost count,” she added.