“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 advisers wrote.

The note, which was obtained by The New York Times, was sent to executives and top political anchors at ABC, CBS, CNN, Fox News and NBC, including star interviewers like Jake Tapper, Chuck Todd and Chris Wallace.

Mr. Giuliani could not immediately be reached on Sunday for comment.