German lawmakers are set to pass legislation Friday to fine social-media companies up to $57 million for failing to quickly delete hate speech, libel and other illegal content, one of the most aggressive efforts in the West to regulate content posted online.

Alphabet Inc.'s Google, Facebook Inc. and civil-rights groups criticized the law, warning it would stifle freedom of speech by encouraging social networks to delete controversial but legal posts. The law, some critics warned, could set the stage for authoritarian regimes to force tech firms to remove more content faster.

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The law, on course to pass through Germany's lower house of parliament Friday, would take effect Oct. 1. Large social networks such as Facebook and Twitter Inc. would be required to delete "clearly illegal" content within 24 hours, while having the ability to set up an industry self-regulating body for processing borderline cases within one week.

The law's quick passage -- the bill was introduced by the Justice Ministry in March -- illustrates the scramble across Europe to ratchet up pressure on tech companies to remove terrorist content and hate speech. It also reflects fears among European politicians that their democracies are vulnerable to propaganda campaigns spread via social media.

The new liability could test Facebook, Google and Twitter's highly automated business models by forcing them to deploy more human expertise to make fine judgment calls on myriad individual posts. How they tackle this challenge could in turn set a costly template for the policing of social network posts world-wide.

"We cannot accept that social networks ignore our laws," German Justice Minister Heiko Maas said. "They can no longer allow their infrastructure to be abused for committing crimes."

But Susan Benesch, who studies ways to fight hate speech at Harvard University's Berkman Center for Internet and Society, said the 24-hour time frame set by the law would lead internet companies to process complaints using algorithms "that are not yet up to the task."

"The German bill would likely push internet companies into massive, over-broad censorship," she said. "We can expect more, even more restrictive laws, in Europe and other parts of the world, especially if the German law passes."

Tech executives, for their part, say they already do a lot to police their platforms for hate speech and terrorist propaganda. But one executive said that the new German law would hurt those efforts by forcing companies to shift resources away from their own efforts to focus on compliance with the German law.

Facebook said it already planned to increase its team examining user complaints to 7,500 from 4,500 world-wide and to more than 700 from 600 for Germany. Earlier this year, it told German parliament the law could lead to "the deletion of legitimate posts" because "even large social networks will not be able to implement completely legally sound and effective processes to examine all complaints within the short time-frame."

Google told the Justice Ministry that it fields 200,000 user complaints globally a day on its YouTube video platform and that the tight deadlines and potential fines would create "a significant incentive to delete any content immediately after a complaint."

Mr. Maas counters that overzealous deletion of posts by social networks isn't a concern because internet companies have a business interest in allowing as much content as possible.

"Social networks won't risk losing their users, who will surely turn away if their posts are constantly being unjustly deleted," Mr. Maas said in a statement.

Mr. Maas in 2015 helped set up a voluntary program in which Facebook, Google and Twitter agreed to delete most hate speech reported by German users within 24 hours. But in March, Mr. Maas said a study commissioned by his ministry had found that Facebook and Twitter were too slow.

The new legislation details 22 sections of the criminal code social networks will have to help enforce. Among them: laws banning libel, character defamation, hate speech, insults against religions, offensive statements and privacy violations.

After the recent terrorist attacks in London and Manchester, British Prime Minister Theresa May called for new regulations, and potentially fines, to force tech firms to remove terrorist propaganda more quickly from their platforms. Later in the month, she was joined by French President Emmanuel Macron, who called tech firms' efforts "insufficient."

But Germany's new law goes farther than any other in Western Europe by forcing tech companies to set up a system for users to flag illegal content and threatening fines for noncompliance. Until now, Brussels and other European governments have generally settled for a voluntary approach.

Indeed, earlier this month, the European Union's executive arm reported improvement from those voluntary efforts, saying that tech companies had boosted removal of illegal content including terrorist propaganda 59% of the time when it was flagged for review, up from a rate of 28% six months ago.

Civil-rights groups, meanwhile, say the German law will embolden undemocratic regimes to make their own efforts to require global social networks to enforce domestic laws.

"This is a great opportunity for authoritarian states," said Johannes Baldauf of the Amadeu Antonio Stiftung, a German foundation that fights hate speech but opposes the legislation.

Deepa Seetharaman in San Francisco contributed to this article.

Write to Anton Troianovski at anton.troianovski@wsj.com and Sam Schechner at sam.schechner@wsj.com

(END) Dow Jones Newswires

June 29, 2017 13:49 ET (17:49 GMT)