A US Senate bill that critics say would enable widespread censorship and surveillance has taken a significant step towards becoming law, raising alarm among internet freedom advocates.

The Senate judiciary committee voted on Thursday to advance the Earn It Act, legislation that on paper is intended to address sexual exploitation. However, privacy experts say the act would give the Department of Justice unprecedented power over the internet and potentially threaten the privacy of messages sent online.

The “Eliminating Abuse and Rampant Neglect of Interactive Technology” (Earn It) Act was introduced in March by the South Carolina Republican Lindsey Graham, Democrat Richard Blumenthal of Connecticut, Republican Josh Hawley of Missouri, and Democrat Dianne Feinstein of California to address what lawmakers characterized as “the rapid increase of child sexual abuse material on prominent online platforms”.

“Technological advances have allowed the online exploitation of children to become much, much worse over recent years,” said Feinstein. “Companies must do more to combat this growing problem on their online platforms.”

The bill would weaken protections under Section 230, a measure that has historically shielded internet publishers from legal responsibility for the content shared on their sites. It would also allow individuals to sue tech companies that don’t take “proper steps” to prevent online child exploitation. Those steps would be determined by a 19-member panel of unelected officials, mostly law enforcement, who would impose a set of “best practices” that websites and online forums would have to follow, or risk getting shut down.

The Earn It Act is supported by anti-exploitation groups including the National Center for Missing & Exploited Children (NCMEC), Rights4Girls, and the National Center on Sexual Exploitation.

But privacy advocates are concerned its powers could overreach and pose a threat to encryption, a tool that obscures the content of messages so others – including tech companies and law enforcement – cannot read them.

If technology companies are to be held liable for content on their sites, the privacy advocates say, they could be required to scan all user messages, requiring a weakening of encryption practices.

“The Earn It Act could end user privacy as we know it,” said the Electronic Frontier Foundation. “Tech companies that provide private, encrypted messaging could have to rewrite their software to allow police special access to their users’ messages.”

Graham’s office did not return request for comment, but it previously said his “goal here is not to outlaw encryption … that will be a debate for another day”. However, Barr – who would be given a large amount of power under the new act – has been outspoken about his desire to force technology companies to allow law enforcement to bypass encryption.

The Earn It act is being compared to the Online Sex Trafficking Act (Fosta) and the Stop Enabling Sex Trafficking Act (Sesta), passed in 2017 to combat online sex trafficking by making websites criminally liable for users’ content. Sesta/Fosta had a chilling effect on internet platforms and put sex workers and members of the LGBTQ+ community in danger, critics said, by forcing them offline. As a result of the acts, Craigslist had to remove its Personals ads section; the website Backpage.com, a classifieds website with a large sex worker presence, was shut down; and social media platforms had to crack down on adult content. Critics argue the legislation broadly censored online speech and negatively affected people who engage in consensual sex work, ultimately helping sex traffickers by pushing the industry underground.

Similarly, the Earn It Act would “undermine the privacy of every single American and stifle our ability to communicate freely online”, the ACLU said in a letter urging senators to vote no on the bill.

Advocates fear the commission created by the Earn It act would recommend “best practices” required by tech companies that disproportionately censor content relating to LGBTQ+ matters, sex work, and the sex industry.

“Our online freedoms are now in serious jeopardy,” said Kate Ruane, ACLU senior legislative counsel, in response to the Senate judiciary committee’s vote.

In recent days, the judiciary committee has tried to sidestep growing opposition to the bill by introducing amendments that are intended to address the concerns but “utterly fail to do so”, said Evan Greer of internet freedoms group Fight for the Future.

“A sneaky bill just got even sneakier,” she said. “If they move ahead with this deeply flawed bill, they’ll be ignoring the voices of experts and the public.”

The bill will now head for a vote on the Senate floor, where it could potentially see a vote in the next few weeks before the chamber’s session ends, on 17 July.