Dr Daryl Balia was suspended as international director of Edinburgh 2010 two days before the conference began after complaining of "bullying and intimidation" and was ordered to stay away from the event which he had spent three years planning.
Now, Dr Balia has announced he will resign from the post and return to South Africa.
Dr Balia said "I was the token black in a very white machinery. I got dismissed. I still have no idea why it happened."
Two leading delegates issued a statement of support for Dr Balia, claiming he had been made a scapegoat.