Catherine Lockerbie, director of the Edinburgh International Book Festival, the biggest event of its kind in the world, is stepping down after nine years in the role.

The departure of Ms Lockerbie, who has suffered from poor health recently and is at present on sick leave, prompted speculation yesterday about who would succeed her at the festival, which is sponsored by The Times.

It is not thought likely that Richard Holloway, the author and leader of the joint board of the Scottish Arts Council and Scottish Screen, who is standing in for Ms Lockerbie, would be interested in taking over the job full-time. Others who may be considered include Roland Gulliver, the festival's programme manager, Adrian Turpin, director of the Borders Book Festival, and Marc Lambert, chief executive of the Scottish Books Trust. Other contenders are Alan Taylor, the editor of the Scottish Review of Books, Rosemary Goring, literary editor at The Herald, and David Robinson, literary editor of The Scotsman.

Ms Lockerbie, a former journalist, became director in 2000 and presided over a period of remarkable growth. The Edinburgh International Book Festival has become the largest of its kind in the world, with 200,000 people attending more than 750 events each year. It has also become internationally renowned as a platform for leading thinkers, attracting authors from about 45 different nations annually.

Ms Lockerbie said that it had been an “unbelievable privilege” to lead the festival. “The Book Festival has been a personal mission of mine, and I have poured every ounce of my energy, passion and thought into what has been an all-consuming role,” she said.

“Following a period of medical leave, I believe this to be a propitious moment to move on to new challenges and opportunities.”

Susan Rice, chairwoman of the Edinburgh International Book Festival said: “Catherine has taken the festival into the major leagues, expanding the size and quality of its programme, the number of visitors and the praise it earns in the public eye.”

Carol Ann Duffy, the Poet Laureate, said Ms Lockerbie has established the Edinburgh International Book Festival as the “finest of its kind” in

the world.

It is thought Ms Lockerbie will officially leave the book festival when her contract runs out at the end of August.

A spokeswoman for the festival said the search to recruit a replacement would be “international”.

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