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

In a series of tweets announcing the new worldwide policy, Twitter chief executive Jack Dorsey said: “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.

Facebook has faced criticism since it disclosed earlier in October that it will not fact-check ads by politicians or their campaigns.

Chief executive Mark Zuckerberg told US Congress last week that politicians have the right to free speech on Facebook.

In Facebook’s earnings conference call – which began less than an hour after Dorsey’s tweet – Zuckerberg issued an impassioned monologue about what he called Facebook’s deep belief “that political speech is important” and stood by the company’s decision to run unchecked political ads.

He denied this choice is financially motivated, saying such ads make up less than half of a per cent of the company’s revenue.

To put that in perspective, he added, Facebook’s recent five billion dollars Federal Trade Commission fine was more than ten times that.

“This is complex stuff. Anyone who says the answer is simple hasn’t thought about the nuances and downstream challenges,” he said.

“I don’t think anyone can say that we are not doing what we believe or we haven’t thought hard about these issues.”

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

In response, Democratic Senator Elizabeth Warren, another presidential hopeful, ran an 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.

Critics have called on Facebook to ban all political ads. This includes CNN chief Jeff Zucker, who recently called the policy of allowing lies ludicrous and advised the social media giant to sit out the 2020 election until it can figure out something better.

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

Twitter currently only allows certified campaigns and organisations 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 15 November.

Twitter’s policy will start on 22 November.

Trump’s campaign manager called Twitter’s change a “very dumb decision” in a statement on Wednesday.

“This is yet another attempt to silence conservatives, since Twitter knows President Trump has the most sophisticated online program ever,” campaign manager Brad Parscale said.