She told Pink News she had thought the channel was “going to be a breath of fresh air” but said the experience became “an absolute nightmare”.
Writing in the Mail+ on Wednesday, Ms Willoughby said: “All I wanted to do was present a passionate defence of trans people (of whom I am one) after a week of unrelenting negative media coverage…”
Ms Willoughby said she decided to quit GB News following an on-screen interaction with Wootton on Sunday.
“I didn’t want to be part of what I considered the demonisation of a section of society with no representation,” she wrote.
GB News presenter Andrew Neil said the channel had been launched to “expose the growing promotion of cancel culture” and give a voice “to those who feel sidelined or silenced”.
The channel, positioned as a rival to the news and current affairs offerings of the likes of BBC and Sky, has signed a series of high profile figures including former Sky Sports presenter Kirsty Gallacher, ex-BBC presenter Simon McCoy and former ITV presenter Alastair Stewart.
GB News has been contacted for comment.