Hundreds of employees at the social network have signed an open letter urging the company to reconsider a policy which allows politicians to make claims not subject to fact-checking in political adverts.
Facebook has said it will not subject most political advertising to fact-checking, instead only banning adverts which contain claims which have been debunked by third-party fact-checkers.
The letter warns that not scrutinising claims made in such adverts could allow politicians to "weaponise" the platform and increase distrust in the site.
According to the New York Times, which published a copy of the letter, Facebook staff called on executives at the company to "hold political ads to the same standards as other ads", arguing that "free speech and paid speech are not the same thing".
It also called on Facebook to make political advertising clearer on the platform, restrict the amount of targeting political campaigns can undertake with adverts and introduce a spending cap for individual politicians purchasing advertising.
Facebook has said it will not censor freedom of expression in political advertising, and earlier this month Mr Zuckerberg used a speech to criticise censorship on the internet and argued that free speech was important to social progress.
In response to the staff open letter, a Facebook spokesman said: "Facebook's culture is built on openness so we appreciate our employees voicing their thoughts on this important topic.
"We remain committed to not censoring political speech, and we will continue exploring additional steps we can take to bring increased transparency to political ads."
The social network's stance has also been questioned by MPs, with Digital, Culture, Media and Sport Committee chair Damian Collins writing to the firm's head of communications, former deputy prime minister Sir Nick Clegg, last week on the issue.
The MP for Folkestone and Hythe said Facebook's policy on political ads dropped a ban on "deceptive, false or misleading content" to instead only address "claims debunked by third-party fact-checkers, or, in certain circumstances, claims debunked by organisations with particular expertise".
In a letter to Sir Nick, Mr Collins asked why Facebook decided to change its policy, "given the heavy constraints this will place on Facebook's ability to combat online disinformation in the run-up to elections around the world".
Earlier this month, US presidential candidate Elizabeth Warren paid for a series of Facebook adverts which included false claims about Mr Zuckerberg to highlight her own concerns over the policy.
The adverts, which successfully appeared on the social network, claimed the Facebook founder had endorsed US President Donald Trump for re-election next year, before suggesting they had given politicians "free rein to lie" on the platform.
"Facebook holds incredible power to affect elections and our national debate," the Democratic candidate said in a Twitter post on the issue.
"They've decided to let political figures lie to you - even about Facebook itself - while their executives and their investors get even richer off the ads containing these lies.
"Once again, we're seeing Facebook throw its hands up to battling misinformation in the political discourse, because when profit comes up against protecting democracy, Facebook chooses profit.
"Facebook already helped elect Donald Trump once through negligence.
"Now, they've changed their policy so they can profit from lies to the American people. It's time to hold Mark Zuckerberg accountable."