Next year's World Athletics Championships in London have lost a third board member after managing director Sally Bolton quit her post.
Fellow board members Heather Hancock and Martin Stewart stood down last week, amid reports of differences with chairman Ed Warner, who is also head of UK Athletics.
But in a statement, Bolton said: "I'm incredibly proud of the work that has been completed in achieving the early milestones that lay the foundations for the event's success."
She continued: "I wish the team well in what is going to be an exciting 18 months, and I look forward to seeing some amazing sport take place at next year's championships."
London 2017 said only that she had resigned for "personal reasons".
Warner added: "Sally has successfully laid the foundations for what will be the best ever World Championships next year and we wish her well for the future."
The championships, being held in London for the first time, take place in July and August next year.