Retired judge Baroness Butler-Sloss has said she is stepping aside as the head of an inquiry into allegations of historical child abuse.
Downing Street said “it was entirely her decision” and a new chair would be appointed within days.
Lady Butler-Sloss has been under pressure to quit from MPs and victims concerned about her family links.
Her late brother, Sir Michael Havers, was attorney general in the 1980s.
Downing Street said it would “take a few days” to appoint a new chairman and appeared to indicate that whoever was chosen would not be so closely linked to the establishment.
David Cameron’s spokesman said there had been no change in the view of the prime minister or Home Secretary Theresa May about Lady Butler-Sloss’s integrity or suitability for the job.
“She has taken the decision to step down as chair of the panel inquiry,” he said. “It is entirely her decision.
“The government’s view hasn’t changed, that she would have done a first-class job as chair. The reasons for her appointment still absolutely stand in terms of her professional expertise and her integrity, which I don’t think has been questioned from any quarter whatsoever, and rightly so.”
No 10 said the decision had not been prompted by suggestions a co-chairman might be appointed to the panel.
Mrs May spoke to Lady Butler-Sloss over the weekend after she was informed of her decision.
BBC political correspondent Norman Smith said questions had been raised over Lady Butler-Sloss’s age – she will be 81 next month.