The Cambridge academic at the centre of a row over the use of Facebook users' private data has dismissed claims the information could have been used to influence voters.
Dr Aleksandr Kogan, who gave the personal information of millions of Facebook users to controversial election consultancy Cambridge Analytica in 2014, told MPs that personality scores he gave to the company were "highly inaccurate" and "made little sense" for political advertising.
"The idea that this data is accurate, I would say, is scientifically ridiculous. The idea that even if you had a lot more data you could make it super accurate is also pretty silly," he said, appearing before the Digital, Culture, Media and Sport select committee on Tuesday.
Dr Kogan insisted that Facebook's tools were capable of helping campaign groups send targeted advertising without the need for more specific information about people's personalities.
In written evidence supplied to the committee before his appearance he wrote: "The Facebook ads platform provides tools and capability to run targeted ads with little need for our work - in fact, the platform's tools provide companies a far more effective pathway to target people based on their personalities than using scores from users from our work."
CA parent company SCL paid Dr Kogan hundreds of thousands of pounds to harvest data from Facebook using a personality survey, which he then processed to make predictions about personality under the company name Global Science Research.
Asked what the value of the work he did for SCL was, Dr Kogan replied: "Based on what we know now, nothing."
CA executives and whistleblowers have previously insisted on the value and effectiveness of their work.
In secret filming by Channel 4 News released in March, CA executives boasted about profiling voters to help politicians target them with social media adverts.
Former CA employees Christopher Wylie and Brittany Kaiser have told the inquiry the company helped Donald Trump and Ted Cruz's 2016 election campaigns, as well as the Brexit campaign group Leave.EU.
Leave.EU denies the claims but pro-Brexit groups Vote Leave and BeLeave, as well as the DUP and Veterans for Britain, spent large portions of their campaign budgets with Aggregate IQ, a company linked to CA which carries out similar work.
Mr Wylie told the inquiry Aggregate IQ "absolutely" had access to the data collected by Dr Kogan, and the company "blasted" a small number of voters with political adverts on social media during the EU referendum.
Earlier in the hearing, Dr Kogan accused former CA chief executive Alexander Nix of lying in his evidence to the committee in February.
Committee chairman Damian Collins asked Dr Kogan to verify answers from Mr Nix about data collected by his company, Global Science Research, and given to CA.
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.
He also cast doubt on the evidence of Mr Wylie, who presented large amounts of evidence about CA to the committee and testified in March.
"Mr Wylie has invented many things," Dr Kogan claimed.
"By March 2015 we had began to suspect that Mr Wylie may not be the most reputable person in the world," he said, calling him "duplicitous".
Facebook's chief technical officer, Mike Schroepfer, will give evidence to the inquiry on Thursday.