Facebook says it is immediately banning US Facebook and Instagram ads that call voting fraud widespread, or election results invalid, or impugn any one method of voting.
The company announced the new rules in a blog post, adding to earlier restrictions on premature claims of election victory.
The move came a day after US President Donald Trump used the first televised debate with Democratic challenger Joe Biden to amplify his baseless claims that the November 3 presidential election will be "rigged."
Trump has been especially critical of mail-in ballots, and he cited a number of small unrelated incidents to argue that fraud was already happening at scale.
Facebook has been under fire for refusing to fact-check political ads more broadly and for not cracking down on rampant misinformation.
Facebook said the new election ad prohibition would include those that "portray voting or census participation as useless/meaningless" or that "delegitimise any lawful method or process of voting or voting tabulation ... as illegal, inherently fraudulent or corrupt."
Facebook also cited ads that call an election fraudulent or corrupt because the result was unclear on election night or because ballots received afterward were still being counted.
Citing hate speech rules, the social media platform also moved on Wednesday to remove Trump campaign ads suggesting immigrants could be a significant source of coronavirus infections.
Meanwhile two federal judges ruled on Wednesday in favour of voting by mail to protect against COVID-19, with one upholding a universal postal voting plan in Montana and the other blocking restrictions on absentee ballots in Alabama.
Australian Associated Press
