Facebook refused to comply with a request from former Vice President Joe Biden’s campaign, opting to allow a Trump ad alleging Biden’s corruption with regard to Ukraine.

Facebook’s head of global elections policy Katie Harbath responded to the Biden team’s request in a letter obtained Tuesday by the New York Times.

Our approach is grounded in Facebook’s fundamental belief in free expression, respect for the democratic process, and the belief that, in mature democracies with a free press, political speech is already arguably the most scrutinized speech there is.

Biden Campaign spokesman TJ Ducklo called Facebook’s response “unacceptable,” adding, “Whether it originates from the Kremlin or Trump Tower, these lies and conspiracy theories threaten to undermine the integrity of our elections in America. It is unacceptable for any social media company to knowingly allow deliberately misleading material to corrupt its platform.”

CNN had already refused to air that ad and at least one other — making no mention of pressure from the Biden campaign — claiming that the decision was based on the content of the ad. (RELATED: CNN Won’t Air Trump’s Ad On Biden’s Ukraine Troubles, Saying It Mocks Anchor Chris Cuomo)

“CNN is rejecting the ad, as it does not meet our advertising standards. Specifically, in addition to disparaging CNN and its journalists, the ad makes assertions that have been proven demonstrably false by various news outlets, including CNN,” the network said in a statement to The Daily Beast.

One of Biden’s Democratic primary opponents, New Jersey Sen. Cory Booker, called for other networks to follow CNN’s lead and refuse to air the ad.

NEW statement from @ASDem calling on TV stations in early states to join @CNN in refusing to air baseless Trump ad attacking Biden. pic.twitter.com/nYh2GRuh0A — Julie McClain Downey (@McClainJulie) October 4, 2019

The Trump campaign responded to CNN’s decision by suggesting that the network was just another arm of the Democratic Party and was working to protect both Biden and his son Hunter.

#CNN won’t run a pair of #Trump2020 ads, claiming the clips contain factual inaccuracies about the #WhistleblowerComplaint and @JoeBiden. The Trump campaign responded by accusing @CNN of being a “Democrat public relations firm” instead of a news channel. https://t.co/NIXlQRdMz6 — The Epoch Times (@EpochTimes) October 4, 2019

Of course @JoeBiden’s national press secretary is applauding @CNN’s decision to protect #QuidProJoe and censor the Trump campaign’s ad on Biden Inc. The establishment media isn’t even pretending to be neutral anymore. CNN might as well change their initials to DNC. pic.twitter.com/MtFkeDcrZL — Donald Trump Jr. (@DonaldJTrumpJr) October 3, 2019

Fox News opted to air the ad, but revealed that the network had been pressured by the Biden campaign to refuse it. “We are not in the business of censoring ads from candidates on either side of the aisle,” the Fox News statement read in part.

“We are not in the business of censoring ads from candidates on either side of the aisle.”@FoxNews rejected a request by the @JoeBiden campaign not to run an advertisement from President Trump’s campaign that targets #Biden’s involvement with #Ukraine. https://t.co/8BhRRV78u5 — The Epoch Times (@EpochTimes) October 5, 2019

The Biden campaign had previously attempted to steer media coverage away from the former vice president and his son by sending out a mass email to multiple outlets and individual anchors, demanding that they refrain from booking Trump attorney Rudy Giuliani to discuss the situation surrounding the July 25 phone call between Trump and Ukrainian President Volodymyr Zelensky.

WATCH the ad in question: