Sandy Parakilas, the platform operations manager at Facebook responsible for policing data breaches by third-party software developers between 2011 and 2012, told the Guardian he warned senior executives at the company that its lax approach to data protection risked a major breach.

“My concerns were that all of the data that left Facebook servers to developers could not be monitored by Facebook, so we had no idea what developers were doing with the data,” he said. Parakilas said Facebook had terms of service and settings that “people didn’t read or understand” and the company did not use its enforcement mechanisms, including audits of external developers, to ensure data was not being misused.

Parakilas, whose job it was to investigate data breaches by developers similar to the one later suspected of Global Science Research, which harvested tens of millions of Facebook profiles and provided the data to Cambridge Analytica, said the slew of recent disclosures had left him disappointed with his superiors for not heeding his warnings. “It has been painful watching,” he said. “Because I know that they could have prevented it.”