Cambridge Analytica's ex-CEO, Alexander Nix, has refused to testify before the U.K. Parliament's media committee, citing British authorities' investigation into his former company's alleged misuse of data from millions of Facebook accounts in political campaigns.

Committee Chairman Damian Collins announced Nix's decision a day before his scheduled appearance but flatly rejected the notion that he should be let off the hook, saying Nix hasn't been charged with a crime and there are no active legal proceedings against him.

"There is therefore no legal reason why Mr. Nix cannot appear," Collins said in a statement. "The committee is minded to issue a formal summons for him to appear on a named day in the very near future."

Nix gave evidence to the committee in February, but was recalled after former Cambridge Analytica staffer Christopher Wylie sparked a global debate over electronic privacy when he alleged the company used data from millions of Facebook accounts to help U.S. President Donald Trump's 2016 election campaign. Wylie worked on Cambridge Analytica's "information operations" in 2014 and 2015.

Wylie has also said the official campaign backing Britain's exit from the European Union had access to the Facebook data.

Cambridge Analytica has previously said that none of the Facebook data it acquired from an academic researcher was used in the Trump campaign. The company also says it did no paid or unpaid work on the Brexit campaign. The company did not respond to requests for comment from The Associated Press on Tuesday.

The Information Commissioner's Office said Tuesday that it had written to Nix to "invite him" to be interviewed by investigators. The office is investigating Facebook and 30 other organizations over their use of data and analytics.

"Our investigation is looking at whether criminal and civil offences have been committed under the Data Protection Act," the office said in a statement.

Nix's refusal to appear comes as the seriousness of the British inquiry becomes more evident.

Facebook has said it directed Cambridge Analytica to delete all of the data harvested from user accounts as soon as it learned of the problem.

But former Cambridge Analytica business development director Brittany Kaiser testified Tuesday that the U.S. tech giant didn't really try to verify Cambridge Analytica's assurances that it had done so.

"I find it incredibly irresponsible that a company with as much money as Facebook ... had no due diligence mechanisms in place for protecting the data of U.K. citizens, U.S. citizens or their users in general," she said.

Kaiser suggested that the number of individuals whose Facebook data was misused could be far higher than the 87 million acknowledged by the Silicon Valley giant.

She told lawmakers that in an atmosphere where data abuse was rife, she believed the leadership of the Leave.EU campaign combined data from members of the U.K. Independence Party and from the customers of two insurance companies, Eldon Insurance and GoSkippy Insurance.

The two executives were then able to create their own "their own Cambridge Analytica" using her proposals, Kaiser testified.

"Arron Banks and Andy Wigmore have told multiple individuals that they took my proposal and copied it and they created their own Cambridge Analytica, which they called Big Data Dolphins in partnership with the data science department at the University of Mississippi," Kaiser said.

The university rejected Kaiser's allegation.

"The assertion that the University of Mississippi has received or analyzed any data from these companies is not true," Alice Clark, vice chancellor for university relations, said in a statement emailed Tuesday to The Associated Press.

Leave.EU's communications director, Andy Wigmore, also called Kaiser's statements a "litany of lies."

It is how the data was used that alarms some members of the committee and has captured the attention of the public.

An expert on propaganda told the committee Monday that Cambridge Analytica used techniques developed by the Nazis to help Trump's presidential campaign, turning Muslims and immigrants into an "artificial enemy" to win support from fearful voters.

University of Essex lecturer Emma Briant, who has for a decade studied the SCL Group — a conglomerate of companies, including Cambridge Analytica — interviewed company founder Nigel Oakes when she was doing research for a book. Oakes compared Trump's tactics to those of Nazi leader Adolf Hitler in singling out Jews for reprisals.

"Hitler attacked the Jews, because ... the people didn't like the Jews," he said on tapes of the interview conducted with Briant. "He could just use them to leverage an artificial enemy. Well that's exactly what Trump did. He leveraged a Muslim."