The House select committee investigating the January 6 insurrection at the Capitol has ordered several social media firms to hand over data relating to the attack, asignificant step toward transparency that could have broader privacy implications.

The committee on Thursday subpoenaed Twitter, Meta, Alphabet and Reddit for private messages exchanged on the platforms about the attack aas well as information regarding moderation policies that allowed communities to remain online even as they incited violence in early 2021.

Congressman Bennie Thompson, the chairman of the select committee, said the committee is seeking to answer two key questions: how the spread of misinformation contributed to the violent attack, and what steps social media companies took to prevent their platforms from “being breeding grounds for radicalizing people to violence”.

The subpoenas mark an escalation in the committee’s efforts to get answers from the tech companies. Thompson added in his letter that the subpoenas came after “months of engagement” with the firms and that the four companies have so far ignored requests for information.

“We cannot allow our important work to be delayed any further,” he said.

The panel in August asked 15 tech companies, including the four subpoenaed on Thursday as well as TikTok, Snapchat, Parler and 4chan, for records related to the riot.

In letters sent this week the tech firms, Thompson lamented their lack of response. In a letter to Meta CEO Mark Zuckerberg, Thompson said that “despite repeated and specific requests for documents” related to Facebook’s practices on election misinformation and violent content, the committee had still not received these materials.

Following the January 6 attack, social media platforms have been scrutinized for amplifying calls to violence, spreading misinformation and serving as an organizing tool for the rioters.

Last March, lawmakers grilled the CEOs of Google, Twitter and Facebook about the platforms’ role in the Capitol riot. And in the months since, the major platforms have all announced initiatives to curb the spread of misinformation through their products.

But still, much about the content moderation policies of major tech firms remains black box, with executives slow to reveal details of how misinformation and hate speech is moderated and how many resources are dedicated to mitigating such issues. Now, increased transparency could come by means of subpoena.

For lawmakers, the problem came even more acutely into focus with papers leaked by whistleblower Frances Haugen in October 2021, which showed how Facebook failed to enforce policies that would rein in hate speech because they were detrimental to its bottom line. Speaking to Congress, Haugen called for more transparency from Facebook and other companies, including an independent oversight board.

In a letter to Zuckerberg, the select committee cited revelations from Haugen, requesting access to the company’s internal analyses of the spread of misinformation and calls to violence relating to the 2020 election.

In particular, the committee requested more information on the “Stop the Steal” movement and how it was regulated. A “Stop the Steal” Facebook group amassed hundreds of thousands of members and was used to coordinate some of the actions on January 6. While Facebook eventually took it down, other related pages stayed online, said Imran Ahmed, CEO of the Center for Countering Digital Hate.

“It is absolutely crucial to understand the decision making process that led to them to leave those pages online – how they executed enforcement of their policies against violence, encouraging violence, intimidation, extremism and hate.”

Similarly, Reddit has been requested to provide information on its community r/The_Donald, which was used to plan the January 6 action before it was banned weeks later on 27 January.

Lawmakers were also seeking materials from Alphabet, the parent company of YouTube, because the video platform hosted significant communications by key players in the Capitol attack, including Trump’s former chief strategist Steve Bannon and rioters livestreaming their movements on January 6.

Activists say the need to hold companies accountable for how their policies contributed to the Capitol riots should be held in balance with civil rights and privacy protections.

The subpoenas may bring up privacy concerns, said Evan Greer, deputy director of digital rights group Fight for the Future. “Forcing companies to hand over private messages of its users could have major privacy implications,” Greer said.

“It’s essential to remember that government surveillance and demands for data from private companies are primarily weaponized against marginalized communities,” they said. “The white supremacists who stormed the Capitol deserve to be held accountable, but we should never cheer on expansions of surveillance or government overreach.”

Twitter, Meta, Alphabet and Reddit did not immediately respond to the Guardian’s request for comment.