U.S. lawmakers should look into increasing liability for online platforms such as Facebook Inc. for ads and other commercial speech, a top House Democrat said on Wednesday.

The comments by Representative Jan Schakowsky of Illinois, chairwoman of a subcommittee that has taken the lead in shaping an online privacy bill, come as a legal shield protecting the companies from lawsuits over third-party content is under increasing attack from both parties in Washington.

Advocates of the legal immunity, known as Section 230 of the Communications Decency Act, have argued it protects free speech online by encouraging social media platforms to leave up controversial content, although it also protects their efforts to remove objectionable posts.

“We must draw bright lines that make clear that commerce is not the same thing and should not be confused with speech,” Schakowsky said during a Wednesday webinar with tech critics. “Making money online and selling advertising is not the same as free speech.”

Schakowsky suggested changes that applied to commercial speech could target other tech companies as well, citing Airbnb Inc., which has used Section 230 to push back on regulations of the short-term rentals that users post on the site. Although Section 230 does not apply to content that Amazon.com Inc. generates itself, the e-commerce giant also has a thriving marketplace for third-party sellers.

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The American Economic Liberties Project, which is allied with Democrats and argues for stepped-up antitrust enforcement, said in a Wednesday policy paper that Google and Facebook should be broken up, face regulation and lose Section 230 immunity if they continue to profit from advertising. The policy group said the companies had a negative effect on democracy.