Theresa May has said she was only recently made aware of claims that Baroness Butler-Sloss' late brother was involved in a cover-up of alleged child abuse.
The Home Secretary was asked about allegations former Attorney General Sir Michael Havers urged an MP not to name an alleged paedophile using Parliamentary privilege.
Ms May said the claims had not been made public or brought to her attention before the appointment of Sir Michael's sister Lady Butler-Sloss to head an inquiry into the protection of children from child abuse.
The Baroness says she did not consider the "difficulties" caused by her background and family connections to the child sex abuse inquiry.
Questions have been raised of former High Court judge Baroness Butler-Sloss since her appointment last week.
22 police officers are now assigned to Operation Fernbridge - the probe into claims of a Westminster cover-up of sex child abuse.