Twitter CEO Jack Dorsey announced in a series of tweets Wednesday the company’s new policy of banning all political advertising from its service. Jose Luis Magana/Associated Press, file

SAN FRANCISCO — Twitter is banning all political advertising from its service, saying social media companies give advertisers an unfair advantage in proliferating highly targeted, misleading messages.

“While internet advertising is incredibly powerful and very effective for commercial advertisers, that power brings significant risks to politics, where it can be used to influence votes to affect the lives of millions,” Twitter CEO Jack Dorsey said Wednesday in a series of tweets announcing the new policy.

Facebook has taken fire since it disclosed earlier in October that it will not fact-check ads by politicians or their campaigns, which could allow them to lie freely. CEO Mark Zuckerberg told Congress last week that politicians have the right to free speech on Facebook.

The issue suddenly arose in September when Twitter, along with Facebook and Google, refused to remove a misleading video ad from President Trump’s campaign that targeted former Vice President Joe Biden, a leading Democratic presidential candidate.

In response, Democratic Sen. Elizabeth Warren, another presidential hopeful, ran her own ad on Facebook taking aim at Zuckerberg. The ad falsely claimed that Zuckerberg endorsed Trump for re-election, acknowledging the deliberate falsehood as necessary to make a point.

We’ve made the decision to stop all political advertising on Twitter globally. We believe political message reach should be earned, not bought. Why? A few reasons…🧵

— jack (@jack) October 30, 2019

Critics have called on Facebook to ban all political ads. These include CNN chief Jeff Zucker, who recently called the company’s policy of allowing lies “absolutely ludicrous” and advised the social media giant to sit out the 2020 election until it can figure out something better.

Google and Facebook did not have immediate comments on Twitter’s policy change.

Montana Gov. Steve Bullock, another Democratic 2020 contender, retweeted Dorsey’s announcement, adding the comment, “Good. Your turn, Facebook.”

Dorsey said the company is recognizing that advertising on social media offers an unfair level of targeting compared to other mediums. It is not about free expression, he asserted.

“This is about paying for reach. And paying to increase the reach of political speech has significant ramifications that today’s democratic infrastructure may not be prepared to handle,” he tweeted. “It’s worth stepping back in order to address.”

Twitter currently only allows certified campaigns and organizations to run political ads for candidates and issues. The latter tend to advocate on broader issues such as climate change, abortion rights and immigration.

The company said it will make some exceptions, such as allowing ads that encourage voter turnout. It will describe those in a detailed policy it plans to release on Nov. 15.

Federal campaigns are expected to spend the majority of advertising dollars on broadcast and cable channels during the 2020 election, according to advertising research firm Kantar, and about 20 percent of the total $6 billion in spending on digital ads.

Twitter’s policy will start on Nov. 22.