The academic at the centre of a row over the use of Facebook data has accused the former chief executive of Cambridge Analytica of lying to the parliamentary inquiry into fake news.
Appearing before the inquiry today, Dr Aleksander Kogan described testimony by Alexander Nix about work the pair conducted together as a "total fabrication".
Damian Collins, chair of the inquiry and the Digital, Culture, Media and Sport select committee, asked Dr Kogan to verify answers from Mr Nix about data collected by his company, Global Science Research, and given to Cambridge Analytica.
Mr Collins said: "I said to [Mr Nix] 'Does any of your data come from Global Science Research?' And he said 'no'."
"That's a fabrication," replied Dr Kogan.
Mr Collins continued: "I said 'They have not supplied you with data or information?' And he said, 'no'."
"Total fabrication," Dr Kogan replied.
Dr Kogan insisted that he did not break the terms and conditions of Facebook in they way he gathered data and shared it with Cambridge Analytica's parent company SCL.
"For you to break a policy it has to exist," he said, adding "I'd agree my actions were inconsistent with the language of this document, but that's slightly different."
Dr Kogan has dismissed the idea that the data he gave SCL could have been used to target political adverts on Facebook as "scientifically ridiculous".
He said: "The idea that this data is accurate, I would say, is scientifically ridiculous.
"The idea that you even if you had a lot more data you could make it super-accurate is also pretty silly."
Instead, he insisted that Facebook's advertising platform is already sufficient.
"You just don't need this data to do that. Facebook gives you everything available to do that."
Asked what the value of the work he did for SCL was, Dr Kogan replied: "Based on what we know now, nothing."