"The Trump campaign is preparing to file suit against Cliff Sims for violating our [non-disclosure agreement]", Glassner said in a statement posted on Twitter.
Earlier on Tuesday, Trump referred to Sims as a low-level staffer that he hardly knew. He went on to say that Sims’ book was based on made up stories and fiction.
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"He pretended to be an insider when in fact he was nothing more than a gofer. He signed a non-disclosure agreement. He is a mess!" Trump said in a statement on Twitter.
Sims’ new tell-all-book, called “Team of Vipers: My 500 Extraordinary Days in the Trump White House”, hit the bookshelves on Tuesday. Advance excerpts have reportedly revealed embarrassing anecdotes about Trump and top White House officials.