Donald Trump continued to trade insults with former aide Omarosa Manigault Newman on Monday night, escalating a made-for-TV spat with the former Apprentice contestant.

As midnight neared, the president tackled Ms Manigault Newman's claim that she had heard an audiotape of him using the N-word.

He tweeted that he had received a call from the producer of "The Apprentice" assuring him "there are NO TAPES of the Apprentice where I used such a terrible and disgusting word as attributed by Wacky and Deranged Omarosa."

Mr Trump insisted: "I don't have that word in my vocabulary, and never have." He said Ms Manigault Newman had called him "a true Champion of Civil Rights" until she was fired.

Ms Manigault Newman, the former White House liaison to black voters, writes in her new memoir that she'd heard such tapes existed. She said on Sunday that she had listened to one after the book closed.