"You know what, I was a viper, I was a part of that team. I did a bunch of things that I wish I would've done different, but I wanted to get into a place that was a really strong team environment," Sims said in an interview on ABC's "Good Morning America." Sims said he left the White House to pursue a job at the State Department, though the White House pushed back on that and said that Sims was fired.
In his new book, "Team of Vipers," Sims also described White House counselor Kellyanne Conway as "a cartoon villain brought to life" and one of the biggest leakers in the White House, which Conway commented on in a statement to Vanity Fair.
"The real leakers, past and present, get much more positive press than I do. While it’s rare, I prefer to knife people from the front, so they see it coming," Conway said in the statement.
Among other details from the book, Sims wrote about sitting with the president and creating a list of "who inside the White House is a problem." Sims said he became close to the president by assisting in his weekly addresses and participating in meetings with foreign and congressional leaders. The White House has denied that Sims was part of the president's inner circle.
Sims described the Trump White House as "a tough place to work," "highly competitive" and full of a "bunch of type A people" with many different ideological agendas.
"Ultimately, that could be a good thing -- you come to good decisions when people with diverse points of view share their opinion -- but ultimately, that only works if when people walk out of that room, they do whatever the decision the president made was and that's where things seem to break down here," Sims said.
Asked what responsibility the president bears for the creation of an environment Sims called a "team of vipers," he said it was part of Trump's style.
"I've heard it said that every president gets the White House that they deserve and I do think that some of the way that he operates, the creative chaos that he -- kind of freewheeling style, his penchant for putting two rival staff members in a room and letting them fight it out over an issue does breathe some of this competitive aspect," Sims said.