WASHINGTON — The academic who helped Cambridge Analytica vacuum up private information from tens of millions of Facebook profiles sued the social media giant on Friday, arguing that the company defamed him when it claimed he had lied about how the data was going to be used.

Since the full scope of Cambridge Analytica’s data mining was revealed last year, Facebook has repeatedly tried to shift blame for the privacy breach onto the academic, Aleksandr Kogan. Facebook executives — including the chief executive, Mark Zuckerberg — have said Mr. Kogan told Facebook that the data was for academic purposes when it was being collected for use in political campaigns.

Mr. Kogan, 32, a former psychology professor, used a quiz app to collect the data, and has insisted that the fine print accompanying his app said the information could be used commercially. That was an outright violation of Facebook’s rules at the time, but the company does not appear to have regularly checked that apps were complying.

“Alex did not lie, Alex was not a fraud, Alex did not deceive them, this was not a scam,” said Steve Cohen, a lawyer for Mr. Kogan. “Facebook knew exactly what this app was doing, or should have known. Facebook desperately needed a scapegoat, and Alex was their scapegoat.”