(CNN) Presumptive Democratic presidential nominee Joe Biden's campaign is calling on Facebook and Twitter to remove false posts sent this week by President Donald Trump about foreign-backed voter fraud and stoking fears of a 'rigged election.'
"Our campaign has sent letters to Twitter and Facebook demanding that this disinformation, which seeks to undermine faith in our electoral process, gets taken down immediately," Biden campaign manager Jen O'Malley Dillon said in a statement.
In the campaign's letter to Twitter, obtained by CNN, the campaign's general counsel Dana Remus scolds the company for not taking action and argues the President's tweets "creates the misimpression that the tens of millions of Americans who will vote by mail may have their votes drowned out by fraud."
Twitter said Monday it would not take action on the President's tweets.
CNN has repeatedly debunked Trump's comments, and his primary allegation -- that voting-by-mail leads to "massive fraud" -- is completely untrue.
The same claims were posted to the President's Facebook account on Monday.
The letters come after the Biden campaign recently escalated its attacks on Facebook over its decision not to remove misinformation and false political advertisements from its platform. Earlier this month, the presumptive Democratic nominee's campaign began a push they are calling #MoveFastFixIt, urging its millions of supporters to sign an open letter to Mark Zuckerberg, the Facebook co-founder and chief executive. The letter, the campaign's latest episode in its battle with Facebook that dates back to last year, calls on Facebook to implement rules that prohibit threatening behavior and lies about how to vote.
In her letter to Facebook, obtained by CNN, Remus commends the social media platform for its Voting Information Center but calls on it to "clarify its existing policies" on spreading election disinformation.
"Now is the time for Facebook to meet its commitment to provide "clear, accurate and authoritative information" to its users on "how to vote this year," Remus writes, quoting Facebook's own pledge.
Facebook has not taken any action on the posts.
"We appreciate the concerns raised by the Biden campaign and look forward to sharing more details about our Voting Information Center, where more Americans will be alerted to accurate, authoritative information about voting than ever before," said Facebook spokesperson Andy Stone.
Last month, Twitter labeled two of the President's tweets that made false claims about mail-in ballots in California. Twitter cited its "civic integrity policy" to support its decision, which includes rules against voter misinformation.
However, Trump's tweets on Monday did not run afoul of those rules, Twitter said, because the President's claims were apparently too vague. The company pointed to its policy which says it will not take action on tweets that contain "broad, non-specific statements about the integrity of elections or civic processes."
The Biden campaign argued that Trump's Monday tweets do violate Twitter's rules, quoting from Twitter's policy that has rules against "false or misleading information intended to intimidate or dissuade people from participating in an election."
Twitter declined to comment specifically on the campaign's demands, pointing instead to a statement made by a company spokesperson Monday that it specifically reviewed three tweets sent by the President on Monday morning and said they were not in violation of the company's rules.
On Tuesday, Twitter put a warning label on a tweet from President Trump in which he warned if protesters tried to set up an "autonomous zone" in Washington DC they would be "met with serious force!"