Twitter has taken the controversial step to ban political advertising from its platform, just weeks before the UK holds a general election.
The policy comes in on 22 November, before Brits go to the polls on December 12th and before next year's US election.
The announcement comes as Facebook is embroiled in a controversy over its decision to exempt ads by politicians from third-party factchecking and from a policy that bans false statements from paid advertisements.
Donald Trump's campaign team has attacked the decision as "very dumb" and "yet another attempt to silence conservatives".
In a series of tweets, Twitter boss Jack Dorsey explained the decision, saying "political message reach should be earned, not bought".
"A political message earns reach when people decide to follow an account or retweet," he said.
"Paying for reach removes that decision, forcing highly optimized and targeted political messages on people. We believe this decision should not be compromised by money.
"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."
Dorsey said internet advertising posed an evolving set of risks such as "micro-targeting, unchecked misleading information, and deep fakes".
Donald Trump's 2020 election campaign called the ban a "very dumb decision for their stockholders" as the firm would lose "hundreds of millions of dollars of potential revenue".
The statement from campaign manager Brad Parscale called it "yet another attempt to silence conservatives, since Twitter knows President Trump has the most sophisticated online programme ever known".
Twitter bans political ads in yet another attempt by the left to silence Trump and conservatives. Wouldn’t be surprised if @twitter lifted the ban after 2020.
— Brad Parscale (@parscale) October 30, 2019
A political message earns reach when people decide to follow an account or retweet. Paying for reach removes that decision, forcing highly optimised and targeted political messages on people. We believe this decision should not be compromised by money.
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.
Dorsey said the firm would reveal the final policy by 15 November, to begin on 22 November.
There will be few exceptions such as ads in support of voter registration.
"This isn't about free expression," said Dorsey. "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. It's worth stepping back in order to address."
For instance, it‘s not credible for us to say: “We’re working hard to stop people from gaming our systems to spread misleading info, buuut if someone pays us to target and force people to see their political ad…well...they can say whatever they want! 😉”
— jack 🌍🌏🌎 (@jack) October 30, 2019
Twitter's shares were down 3% in after-hours trading as investors reacted to the news.
The issue of political ads flared up again in September when Twitter, Facebook and Google refused to remove a misleading video from Donald Trump's campaign that targeted former vice president Joe Biden - his likely opponent in next year's US election.
Yuval Ben-Itzhak, CEO of Socialbakers shares his thoughts on why Twitter might have taken this step, and what this means for the platform – which has put lots of time and energy into cleaning itself up in the past year.
“Twitter has worked hard over the last year to clean up its platform to make it a safer, more enjoyable place for its users. By banning political advertising on the platform, Twitter's leadership is taking an important stance, " Ben-Itzhak said.
“Validating each ad at scale is technically challenging to say the least, so by banning politically-motivated ads the platform stands a better chance of remaining free of ‘digital pollution’ for its advertisers and users."