Harry Potter creator JK Rowling has "terminated" her association with the literary agent who helped to launch her first book on the boy wizard.

Rowling, one of the richest women in the world, had worked with Christopher Little since he found a publisher for her first novel Harry Potter and the Philosopher's Stone in August 1996.

The books have sold more than 400 million copies and been translated into 67 languages.

A statement issued by StonehillSalt PR on behalf of JK Rowling said: "This was a painful decision, especially as Ms Rowling had actively sought a different outcome for some weeks. However, it was not taken without good reason and it finally became unavoidable."

Last month Rowling revealed previously unpublished Harry Potter material would be released on a new website in a move she described as a "give-back" to her millions of fans.

The interactive website, which includes elements of social networking and computer games, allows fans to access material cut from the original books and read new insights from the author along the way. Potter fans could register from June 23 for an online challenge that goes live on the website on July 31.