Escalating his attacks on Silicon Valley, President Donald Trump hinted Thursday at new regulations on social media as he gathered critics of major online platforms at a White House "summit."
Trump invited conservative activists who have been curbed or banned on social media to press his argument that big social networks are discriminating against conservatives, notwithstanding his large online following.
"A big subject today at the White House Social Media Summit will be the tremendous dishonesty, bias, discrimination and suppression practiced by certain companies. We will not let them get away with it much longer," Trump tweeted.
The comments stoked fears that the White House may seek to eliminate the legal framework that protects online services from liability over harmful content posted by others but hosted on their platforms.
Digital rights activists and others warned that removing the protection - codified as Section 230 of a 1996 law - could undermine free speech protections and harm the internet ecosystem.
"The government shouldn't require - or coerce - intermediaries to remove constitutionally protected speech that the government cannot prohibit directly," said a letter signed by 27 civic and digital rights organisations and 50 legal scholars.
The letter said such demands would violate the US constitution's First Amendment on free expression.
"Also, imposing broad liability for user speech incentivises services to err on the side of taking down speech, resulting in overbroad censorship - or even avoid offering speech forums altogether," it added.
Trump has repeatedly claimed that firms such as Facebook, Google and Twitter - who were not invited to the summit - discriminate against him and his supporters, even though his own Twitter account has nearly 62 million followers.
Big internet firms have roundly denied accusations of political bias.
But they also have faced pressure from governments around the world to remove abusive and hateful content as well as conspiracy theories, such as those promoted by Trump and his allies attending Thursday's White House gathering.
Twitter said last month it would add warnings to tweets from officials and politicians that violate its rules - a move potentially impacting Trump's prodigious output.
The Computer & Communications Industry Association, a trade group whose members include Facebook and Google, said the White House event "seems designed to intimidate companies to bias content in favor of whoever is calling the meeting."
"No private company should be browbeaten by the government into giving a pass to objectionable content that violates company policies," CCIA president Ed Black said in a statement.
"Social media sites may wish to allow many types of speech, but should not be required to stay neutral on hate or religious intolerance.
"If those airing grievances at this week's meeting are unsatisfied with one company's policy against objectionable content, there are plenty of competitors from which to choose."
Without the tech platforms, Thursday's event is "less of a summit and more of a complaining festival," Adam Chiara, a University of Hartford professor of communication told AFP this week.
"A summit usually involves parties talking about how to reach a goal or discussing ways to meet objectives. That will be hard for President Trump to do without having the mega social media platforms there."
Daniel Castro, vice president of the Information Technology and Innovation Foundation, a think tank focused on the tech sector, said the gathering "gives some of these more eccentric characters a veneer of legitimacy" which could dissuade online services from deactivating their accounts over inappropriate content.