Rudy Giuliani, the president’s personal attorney, responded Sunday to the Biden campaign's demand that TV networks discontinue booking him, saying the Biden camp wants to silence him out of fear of the questions he is raising about the former vice president and his son.

"I've never heard of a candidate saying that a critic, demanding that the media shut down and silence someone who is raising legitimate questions about him," Giuliani told the Washington Examiner. "Remember, I believe the reason for it is that, today, I didn't just raise questions. I produced something that the other side has never had — an affidavit from a witness under oath, not a completely wrong anonymous witness."

He continued, "The one thing about corrupt politicians is, they're used to lying and they're used to a fawning press, particularly if they're Democrats ... and they cannot handle the fact if somebody is standing up to them, so they're sending their Democratic media to find anything they can find to spoil my reputation. All they're trying to do is kill the messenger and silence the messenger. But they're not answering the message."

In an effort to keep the former New York City mayor from talking about Joe Biden and his son, Hunter Biden, in relation to Ukraine on broadcast TV, the Biden campaign sent a letter Sunday to ABC, CBS, NBC, CNN, and Fox News claiming Giuliani “will knowingly and willingly lie in order to advance his own narrative.”

“While you often fact check his statements in real time during your discussions, that is no longer enough. By giving him your air time, you are allowing him to introduce increasingly unhinged, unfounded and desperate lies into the national conversation,” the Biden campaign wrote in a letter.

The letter continues, “We write to demand that in the 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.”

Trump’s opponents have criticized the president, threatening impeachment, for allowing Giuliani to urge Ukraine to investigate potential U.S. election meddling by the nation during the 2016 campaign and whether Biden pressured Ukrainian leadership to fire its top prosecutor, Viktor Shokin, in an effort to stop him from investigating corruption related to Burisma Holdings, a firm that employed Biden’s son as a board member.

The Trump White House points to a 2018 video showing the elder Biden bragging about threatening to hold back $1 billion in U.S. loan guarantees if Ukraine did not terminate Shokin from his post. Giuliani defended the president’s July 25 phone call with Ukrainian President Volodymyr Zelensky Saturday, saying it would have been unconstitutional had he not suggested to investigate allegations of corruption by the former vice president.

"The affidavit that I produced today is from a man that's willing to testify in court against him under oath. And say that he intimidated the president of Ukraine, bribed him, extorted him, and got him to fire the prosecutor in order to fix the case against his son and it actually happened," Giuliani said.

He continued, "He could also testify that everything they are saying is false. There never was an investigation of [Hunter] Biden. If there was, by the way, let them produce the report. There is no report. They have lied and said that Hunter Biden was not under investigation or that the Burisma case was closed. This sworn affidavit says just the opposite. I think they are shook to their core, which I must say, reminds me of my investigations of corruption in the '70s and the '80s."

Giuliani added, "The double standard in this country for Democrats and Republicans is so great, not only will they not investigate Democrats for things that they would exaggerate against a Republican, Democrats actually think they can direct the press to do what they want because they've gotten away with that for years."