Author Sir Philip Pullman has resigned as president of the Society of Authors in the wake of a controversy over his support for an author who was accused of racial and ableist stereotyping.
Last year, the His Dark Materials writer backed Kate Clanchy after her memoir attracted criticism.
The society, a trade union for authors, distanced itself from his comments.
He has now said he "would not be free to express my personal opinions as long as I remained president".
Sir Philip took up the post in 2013 but divisions arose last August when he described Clanchy's Some Kids I Taught and What They Taught Me as "humane, warm, decent, generous, and welcoming".
And in response to a tweet he wrongly thought to be about Clanchy, he said people who don't read a book before they condemn it would "find a comfortable home in Isis or the Taliban".
The society said his comments were "not in the name of the Society of Authors" and asked its members to "be mindful of privilege and of the impact of what they create, do and say".
Difference of opinion
Sir Philip later tweeted an apology, saying criticism of Clanchy was "reasonable and balanced" and the "experiences and imaginations" of people of colour "deserve every kind of respect".
In his resignation letter, which has just been published, he said: "Recent events have made it apparent that when a difference of opinion arises, there is no easy way to resolve it within the constitution or the established practices of the Society.
"When it became clear that statements of mine were being regarded as if they represented the views of the Society as a whole (although they did nothing of the sort, and weren't intended to), and that I was being pressed by people both in and out of the Society to retract them and apologise, I realised that I would not be free to express my personal opinions as long as I remained President.
"That being the case, with great regret and after long consideration I chose to stand down."
The society's chief executive Nicola Solomon said: "We were very sorry when Philip told us in February that he intended to resign, and regret that his personal views have come under so much scrutiny because of his presidency of the SoA.
"Social media has changed the way we all communicate, organisations as well as individuals.
"We are in the process of reviewing the constitution to reflect the times in which we live, including the roles of the management committee, chair and president."
In January, Pan Macmillan and Clanchy parted company "by mutual consent", with the publisher saying it would not publish Clanchy's new titles nor any updated editions from her, and would revert the rights and cease distribution, following criticism of Some Kids I Taught and What They Taught Me