Sandy Parakilas, who was platform operations manager at the company from 2011 to 2016 and now works as a product manager for Uber, told  The Guardian that he had told senior executives the firm's approach to data security would prove a major risk.

In recent days, Facebook has had to battle claims that data breaches led to information about 50 million of its users being siphoned off by Cambridge Analytica, a voter-profiling company that worked on Donald Trump’s election campaign.

The company has contested this, saying that the data exfiltration was due to a feature in an app. The allegations about Cambridge Analytica were made by a former employee, Christopher Wylie, and reported by London's The Observer and The New York Times over the weekend.

Parakilas, who was tasked with looking into data breaches by developers, was quoted as saying: "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 the recent disclosures had left him disappointed with his bosses for not acting on his admonitions.

“It has been painful watching because I know that they could have prevented it," he said.

Parakilas alleged that Facebook had no control over data given to outside developers: "Zero. Absolutely none. Once the data left Facebook servers there was not any control, and there was no insight into what was going on.”

He said one executive at the company had advised him against looking too carefully at how data was being used.

Parakilas said he was told, "“Do you really want to see what you’ll find?”, a comment he took to mean that, “Facebook was in a stronger legal position if it didn’t know about the abuse that was happening."