More than 250 Facebook employees have written to founder and CEO Mark Zuckerberg in protest over the social network's policy when it comes to fact checking the content of political ads.

The company has come under fire in recent weeks for a refusal to take down an advertisement from the Trump campaign that made objectively false claims about a political rival, and potential democratic opponent in the 2020 general election, Joe Biden.

At the time Facebook said its fundamental belief in �free expression' justified the decision not to remove the advertisement, despite the company's supposed commitment to combatting the fake news epidemic, which critics say swung the 2016 election in President Trump's favour.

However, now employees at the firm have raised objections to the policy directly with Zuckerberg and other members of the leadership team, by signing a letter calling for the company to reverse course, or risk further damaging the firm's integrity and shattered reputation.

In the letter obtained by the New York Times the employees say the policy has the potential to further damage trust in Facebook and undo the work being done by the company to do a better job of protecting against possible interference in the 2020 election.

It reads: "We're reaching out to you, the leaders of this company, because we're worried we're on track to undo the great strides our product teams have made in integrity over the last two years. We work here because we care, because we know that even our smallest choices impact communities at an astounding scale. We want to raise our concerns before it's too late.

Free speech and paid speech are not the same thing.

"Misinformation affects us all. Our current policies on fact checking people in political office, or those running for office, are a threat to what FB stands for. We strongly object to this policy as it stands. It doesn't protect voices, but instead allows politicians to weaponize our platform by targeting people who believe that content posted by political figures is trustworthy."

Instead, the employees are suggesting Facebook treats political ads in the same way it treats other advertisements when it comes to misinformation. "We should not accept money for political ads without applying the standards that our other ads have to follow," the letter ads.

The employees also suggest stronger visual design treatment for political ads to make them more distinguishable from standard posts. It also calls on the firm to restrict targeting of users, while introducing spend caps for individual politicians.

The employees begin the letter by saying they were proud to work for Facebook. It ends the letter by saying: "This is still our company."