WASHINGTON – Former Vice President Joe Biden’s presidential campaign urged top TV network executives Sunday to stop booking Rudy Giuliani on their shows, accusing President Donald Trump’s personal attorney of introducing “increasingly unhinged, unfounded and desperate lies into the national conversation.”

In an email sent Sunday obtained by USA TODAY, Biden senior adviser Anita Dunn and deputy campaign manager Kate Bedingfield wrote that live fact-checking during Giuliani’s appearances is “no longer enough.”

“We are writing today with grave concern that you continue to book Rudy Giuliani on your air to spread false, debunked conspiracy theories on behalf of Donald Trump,” the two wrote. “By giving him your air time, you are allowing him to introduce increasingly unhinged, unfounded and desperate lies into the national conversation.”

“We write to demand that in service to the facts, you no longer book Rudy Giuliani, a surrogate for Donald Trump who has demonstrated that he will knowingly and willingly lie in order to advance his own narrative,” the email continued.

The networks that received the letter included NBC News, CBS News, Fox News and CNN, according to The Daily Beast, which first reported the letter.

Giuliani Sunday morning made the rounds on several Sunday morning shows, including Fox News’ Sunday Morning Futures, ABC’s This Week and CBS’s Face the Nation. During several of his appearances, Giuliani repeatedly pushed that Biden should be investigated in the ousting of Viktor Shokin, the former General Prosecutor of Ukraine.

Last week, a whistleblower’s complaint was made public that express concern that Trump “used the power of his office” to solicit foreign help to discredit Biden during a call with Ukraine President Volodymyr Zelensky in July. Giuliani is a central figure in the scandal, which has led to the opening of an impeachment inquiry into Trump.

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Dunn and Bedingfield argue in their letter that if Giuliani is booked on a show, then a Biden campaign official should be given the same amount of time on the program. They noted that although networks push back in real-time, it is hard to catch up to Giuliani’s “falsehoods and disinformation.”

“Your obligation is to provide the American people with an informed, fact-based and responsible coverage and debate of critical issues,” they wrote. “Rudy Giuliani has made very clear that his only obligation is to protect Donald Trump, and that he will willingly lie to do so.”

“Giving Rudy Giuliani valuable time on your air to push these lies in the first place is a disservice to your audience and a disservice to journalism,” the letter concluded. “We ask that you no longer book him on your air.”