WASHINGTON — The House committee investigating the Jan. 6 attack on the Capitol issued subpoenas on Thursday to four major social media companies — Alphabet, Meta, Reddit and Twitter — criticizing them for allowing extremism to spread on their platforms and saying they have failed to cooperate adequately with the inquiry.

In letters accompanying the subpoenas, the panel named Facebook, a unit of Meta, and YouTube, which is owned by Alphabet’s Google subsidiary, as among the worst offenders that contributed to the spread of misinformation and violent extremism. The committee said it had been investigating how the companies “contributed to the violent attack on our democracy, and what steps — if any — social media companies took to prevent their platforms from being breeding grounds for radicalizing people to violence.”

“It’s disappointing that after months of engagement, we still do not have the documents and information necessary to answer those basic questions,” said the panel’s chairman, Representative Bennie Thompson, Democrat of Mississippi.

The committee sent letters in August to 15 social media companies — including sites where misinformation about election fraud spread, such as the pro-Trump website TheDonald.win — seeking documents pertaining to efforts to overturn the election and any domestic violent extremists associated with the Jan. 6 rally and attack.

After months of discussions with the companies, only the four large corporations were issued subpoenas on Thursday, because the committee said the firms were “unwilling to commit to voluntarily and expeditiously” cooperating with its work. A committee aide said investigators were in various stages of negotiations with the other companies.

In the year since the events of Jan. 6, social media companies have been heavily scrutinized for whether their sites played an instrumental role in organizing the attack.

In the months surrounding the 2020 election, employees inside Meta raised warning signs that Facebook posts and comments containing “combustible election misinformation” were spreading quickly across the social network, according to a cache of documents and photos reviewed by The New York Times. Many of those employees criticized Facebook leadership’s inaction when it came to the spread of the QAnon conspiracy group, which they said also contributed to the attack.

Frances Haugen, a former Facebook employee turned whistle-blower, said the company relaxed its safeguards too quickly after the election, which then led it to be used in the storming of the Capitol.

Critics say that other platforms also played an instrumental role in the spread of misinformation while contributing to the events of Jan. 6.

In the days after the attack, Reddit banned a discussion forum dedicated to former President Donald J. Trump, where tens of thousands of Mr. Trump’s supporters regularly convened to express solidarity with him.

On Twitter, many of Mr. Trump’s followers used the site to amplify and spread false allegations of election fraud, while connecting with other Trump supporters and conspiracy theorists using the site. And on YouTube, some users broadcast the events of Jan. 6 using the platform’s video streaming technology.

Representatives for the tech companies have been in discussions with the investigating committee, though how much in the way of evidence or user records the firms have handed over remains unclear.

The committee said letters to the four firms accompanied the subpoenas.

The panel said YouTube served as a platform for “significant communications by its users that were relevant to the planning and execution of Jan. 6 attack on the United States Capitol,” including livestreams of the attack as it was taking place.

“To this day, YouTube is a platform on which user video spread misinformation about the election,” Mr. Thompson wrote.

The panel said Facebook and other Meta platforms were used to share messages of “hate, violence and incitement; to spread misinformation, disinformation and conspiracy theories around the election; and to coordinate or attempt to coordinate the Stop the Steal movement.”

Public accounts about Facebook’s civic integrity team indicate that Facebook has documents that are critical to the select committee’s investigation, the panel said.

“Meta has declined to commit to a deadline for producing or even identifying these materials,” Mr. Thompson wrote to Mark Zuckerberg, Meta’s chief executive.

The panel said it was focused on Reddit because the platform hosted the r/The_Donald subreddit community that grew significantly before migrating in 2020 to the website TheDonald.win, which ultimately hosted significant discussion and planning related to the Jan. 6 attack.

Investigators said Twitter subscribers used the platform for the planning and execution of the assault on the Capitol, and Twitter was reportedly warned about potential violence being planned on the site. Twitter users also engaged in communications amplifying allegations of election fraud, including those made by Mr. Trump.

“Unfortunately, the select committee believes Twitter has failed to disclose critical information,” the panel stated.

In recent years, Big Tech and Washington have had a history of butting heads. Some Republicans have accused sites including Facebook, Instagram and Twitter of silencing conservative voices.

The Federal Trade Commission is investigating whether a number of tech companies have grown too big, and in the process abused their market power to stifle competition. And a bipartisan group of senators and representatives continues to say sites like Facebook and YouTube are not doing enough to curb the spread of misinformation and conspiracy theories.

Google said in a statement that it had been cooperating with the committee and that the company had “strict policies prohibiting content that incites violence or undermines trust in elections” that it had enforced before and after Jan. 6.

Meta said that it had “produced documents to the committee on a schedule committee staff requested — and we will continue to do so.”

A spokeswoman for Twitter declined to comment.

A Reddit spokeswoman said the firm had received the subpoena and “will continue to work with the committee on their requests.”

The panel has interviewed more than 340 witnesses and issued dozens of subpoenas, including for bank and phone records.