US congressional investigators want the head of data firm Cambridge Analytica to testify again before their committee, under subpoena if necessary, after a whistleblower claimed the company exploited Facebook and received millions of people’s profiles that were taken without authorisation.

Adam Schiff, the top Democrat on the House intelligence committee, called for the company to be “thoroughly investigated” and said Facebook must answer questions about how it came to provide private user information to an academic with links to Russia.

Democrats have also called for the Facebook CEO, Mark Zuckerberg, to testify before the Senate judiciary committee about what the social media company knew about the misuse of its data.

Cambridge Analytica – owned by the hedge fund billionaire Robert Mercer and formerly headed by sometime Trump adviser Steve Bannon – was suspended pending further information by Facebook on Friday amid the allegation it received personal details from more than 50 million users without their consent.

Whistleblower Christopher Wylie, 28, a former employee who worked with an academic at Cambridge University to obtain the data, told the Observer how it was used to build a software program to predict and influence voters’ choices.

The Republican majority on the House intelligence committee announced this week they were winding up their investigation into Russia’s election interference, concluding there was no collusion with the Trump campaign and, even more controversially, that Moscow did not seek to assist him. Schiff fiercely condemned that decision and said the Democratic minority would continue working on prescriptions for protecting the country in the future.

“This raises serious questions about the level of detail that Cambridge Analytica knew about users, whether it acquired that information illegally and whether it sought to abuse that information in support of President Trump’s political campaign in the United States or Brexit in the United Kingdom,” he told the Guardian.

“The company has repeatedly touted its ability to influence voters through ‘psychographic’ targeting and has claimed it was the fundamental reason that Donald Trump won the 2016 election. Indeed, it may be that through Cambridge Analytica, the Trump campaign made use of illegitimately acquired data on millions of Americans in order to help sway the election.”

The data was collected in early 2014 through a Facebook app that purported to be a psychological research tool called thisisyourdigitallife, built by academic Aleksandr Kogan separately from his work at Cambridge University, the Observer reported. Hundreds of thousands of users were paid to take a personality test and agreed to have their data collected for academic use. Kogan was also an associate professor at St Petersburg State University and received grants from the Russian government to research Facebook users’ emotional states.

Schiff said: “Reports that an American professor with links to Russia was at the centre of this illicit transfer of information raises further questions, which the committee must investigate. Despite our request, and as set out in our status report, the committee has not had the opportunity to talk with numerous Cambridge Analytica personnel who may have knowledge of this and other issues – they must now be brought in for interviews.”

The congressman called for Alexander Nix, the chief executive of Cambridge Analytica, to return “if necessary under subpoena”, noting that he had only spoken to the committee via video link on a day when members were interrupted by votes.

“The committee would also greatly benefit by hearing from the whistleblower named in today’s report, Christopher Wylie, and we plan to reach out to him in the coming days,” Schiff said.

The month after his firm was hired by the Trump campaign, Nix emailed the WikiLeaks founder, Julian Assange, for help tracking down emails Hillary Clinton supposedly had deleted from her private server, the Daily Beast and the Wall Street Journal reported last year. Nix has denied any involvement in Russian election interference.

The data breach was one of the biggest in Facebook’s history and renewed scrutiny of the social network’s influence on the 2016 election. Schiff said: “Facebook must also answer important questions about why it provided private user information to an academic, how they have informed users in advance of these kinds of data transfers and whether it can demonstrate that this data has indeed been destroyed.

“They must also answer questions about how they have notified users about this breach of their personal data. Facebook’s decision to suspend their relationship with Nix and the professor is the right one, but they must explain the long delay in doing so and how they will ensure the protection of users from malicious access to their personal information.”

The Democratic senator Amy Klobuchar, a ranking member of the Senate rules committee with oversight jurisdiction over federal elections, said: “It’s clear these platforms can’t police themselves”.”

“They say ‘trust us’, but Mark Zuckerberg needs to testify before the Senate judiciary committee about what Facebook knew about misusing data from 50 million Americans in order to target political advertising and manipulate voters,” she said.

Facebook’s vice-president and deputy general counsel, Paul Grewal, announced in a blogpost the suspension of Cambridge Analytica pending further information for violating data privacy policies. He wrote that, in 2015, Facebook learned that Kogan passed on data on app users – which included details such as likes and location – to Cambridge Analytica and others. Despite assurances at the time that the data had been destroyed, the social media company was informed in recent days that this had not happened.

Senator Mark Warner, the top Democrat on the Senate intelligence committee, joined the condemnation.

“This story is more evidence that the online political advertising market is essentially the wild west,” he said. “Whether it’s allowing Russians to purchase political ads, or extensive micro-targeting based on ill-gotten user data, it’s clear that, left unregulated, this market will continue to be prone to deception and lacking in transparency.”

It demonstrated the need for Congress to pass legislation to bring transparency and accountability to online political ads, Warner said.

The Massachusetts attorney general said her office was launching an investigation. “Massachusetts residents deserve answers immediately from Facebook and Cambridge Analytica,” Maura Healey said on Twitter in a post that linked to a New York Times article.

The UK’s Information Commission also announced on Saturday that it was conducting an investigation into Cambridge Analytica . The information commissioner, Elizabeth Denham, said: “Any criminal and civil enforcement actions arising from the investigation will be pursued vigorously.”

Trump’s campaign hired Cambridge Analytica in June 2016 and paid it more than $6.2m, according to Federal Election Commission records.

Cambridge Analytica has denied any wrongdoing. It said its contract with Kogan’s company, Global Science Research (GSR), stipulated that Kogan should seek informed consent for data collection and it had no reason to believe he would not.

“When it subsequently became clear that the data had not been obtained by GSR in line with Facebook’s terms of service,” the company said, “Cambridge Analytica deleted all data received from GSR.”

It added: “We worked with Facebook over this period to ensure that they were satisfied that we had not knowingly breached any of Facebook’s terms of service and also provided a signed statement to confirm that all Facebook data and their derivatives had been deleted.

“No data from GSR was used by Cambridge Analytica as part of the services it provided to the Donald Trump 2016 presidential campaign.”