Former White House staff Omarosa Manigault Newman said she walked in on the incident following one of Donald Trump’s meeting with his lawyer.
She makes the claims in her new book Unhinged: An Insider Account of the Trump White House.
According to a section of the book seen by the Washington Post, Ms Newman says: “I saw him put a note in his mouth.
“Since was ever the germaphobe, I was shocked he appeared to be chewing and swallowing the paper.
“It must have been something very, very sensitive.”
Newman was the most senior black employee at the White House, however, she was fired in December by the President’s Chief of Staff, John Kelly.
She has been blasted by current Press Secretary Sarah Huckabee Sanders, who said in a statement Newman was a “disgruntled former White House employee” who was “trying to profit off false attacks”.
However, Ms Newman further criticised the president, saying he “thrives” on drama and comments about him on social media.
She writes in her book: “All we need to remember is that Trump loves the hate.
“He thrives on criticism and insults.
“He delights in chaos and confusion.
“Taking to Twitter to call him names only fuels him and riles his base/
“To disarm him, starve his ego; don’t feed into it.
Ms Newman has known Trump for more than a decade, and worked alongside him before his presidency.
She starred with him in The Apprentice, before taking up a role as assistant to the president which she held for a year.
The former aide claims she was offered a contract of $15,000 (£11,750) every month to stay silent after she was removed from her post at the end of this year.
The contract, seen by the Washington Post, said Ms Newman could not make any comments about Trump, Vice President Mike Pence, or their families which could be damaging.
The non-disclosure agreement offered her work in “diversity outreach” in exchange for the cash.