President Donald Trump’s former chief of staff, retired Marine Gen. John Kelly, has slammed the president as “the most flawed person I have ever met” in private remarks to his friends, according to CNN. Kelly’s comments about Trump will be featured in a CNN special that will air Sunday evening, "The Insiders: A Warning from Former Trump Officials.”

"The depths of his dishonesty is just astounding to me. The dishonesty, the transactional nature of every relationship, though it's more pathetic than anything else. He is the most flawed person I have ever met in my life," Kelly said of Trump.

This was not the first report of Kelly slamming Trump. According to the Washington Post and NBC News, Kelly called Trump “an idiot” and thought he was "unhinged."

Kelly, 70, served as Trump's chief of staff for roughly 17 months.

The Sunday special will feature former Health and Human Services immunologist Rick Bright, former National Security Adviser John Bolton and former Department of Homeland Security general counsel John Mitnick. The ex-Trump officials will spell out why they believe the current president is unfit for office.

Trump has been frequently lambasted by former members of his administration.

Former White House Communications Director Anthony Scaramucci has described Trump as "off the rails" and "mentally declining." Former Secretary of State Rex Tillerson has called Trump “undisciplined,” saying he “doesn’t like to read.”

Former Secretary of Defense James Mattis said Trump "is the first president in my lifetime who does not try to unite the American people — does not even pretend to try. Instead, he tries to divide us.” Former National Security Adviser H.R. McMaster has attacked Trump’s policy of pursuing negotiations with the Taliban, calling it "unwise."

Trump has usually brushed off the criticisms, and launched attacks of his own. For example, he called Tillerson “dumb as a rock” and described Mattis as “the world’s most overrated general.”