Facebook’s outgoing head of public policy and communications, Elliot Schrage, has taken the blame for hiring the controversial PR firm Definers that pushed criticism of the social network’s rivals. The admission came in an internal memo obtained by TechCrunch, in which Schrage defended the use of the firm to conduct opposition research. However, he also admitted that his department’s system for escalating complaints had failed, and expressed regret at having let the company down. Schrage announced his departure from Facebook well before the Definers scandal, making him a convenient out for the beleaguered company.

The use of the firm Definers has drawn fierce criticism after it emerged in a New York Times report that the PR firm had used political campaign tactics to pitch negative stories about Facebook’s competitors including Apple and Google. The firm also pushed information linking the financier George Soros to the anti-Facebook Freedom From Facebook group — a move that the group labeled anti-Semitic. Schrage clarified that the firm had not been used to “distribute or create fake news,” despite the existence of what’s been described as an “in-house fake news shop” owned by Definers.

Schrage, who reports directly to Facebook COO Sheryl Sandberg, took the decision to step down in the wake of the Cambridge Analytica scandal back in June and is due to be replaced next year by former UK deputy prime minister Nick Clegg. The executive is the only high profile executive to have departed Facebook over the company’s scandals this year. In an interview last night with CNN, Zuckerberg reiterated that he has no plans to step down personally, or to remove Sheryl Sandberg from her role as the company’s Chief Operating Officer.