Cambridge Analytica has been ordered to turn over information it has on US citizen David Carroll by the UK's data protection watchdog.
Prof Carroll then launched legal action to find out more, as he believed the information sent to him was incomplete. Cambridge Analytica had previously boasted that every voter profile it generated used 4,000 to 5,000 data points.
As the company named as Cambridge Analytica's data controller, SCL Elections, was based in the UK, Prof Carroll launched legal action at the High Court in London and also filed a complaint with the UK Information Commissioner's Office.
"This should solve a lot of mysteries about what the company did with data and where it got it from," he told the Guardian newspaper.
The High Court case is due to be heard in the next few months.
In a letter sent to the firm, the Information Commissioner said it wanted to know where the data on Mr Carroll came from and what had been done with it.
"The company has consistently refused to co-operate with our investigation into this case and has refused to answer our specific enquiries in relation to the complainant's personal data," Information Commissioner Elizabeth Denham said in a statement.
Cambridge Analytica, which has repeatedly said it did nothing wrong in the way it processed data, is under fire for allegedly using the personal information of millions of Facebook users for political campaigning, without their consent or knowledge.
Neither Cambridge Analytica nor SCL Elections have responded to a request for comment on the ICO demand.
Last week, bankruptcy proceedings were started for Cambridge Analytica and SCL Elections. In a statement, the blame for the closure was put on a "siege of media coverage" that had hit the two companies in the wake of the Facebook data-harvesting scandal.