Lowell Goddard, a High Court judge in New Zealand, also reassured MPs that she was not part of the “establishment” because it does not exist in her home country.
The inquiry has already lost two potential heads, Baroness Butler-Sloss and Dame Fiona Woolf, who stood aside amid concerns over their establishment links.
Judge Goddard, the third chair-designate of the Statutory Inquiry into Child Sexual Abuse, told the Home Affairs Select Committee she was reluctant to set a timescale for the inquiry before she had “scoped” what needed to be done but it had been indicated when she took the job on that it could take “three years, possibly into a fourth”.
She added: “Given the breadth of the subject matter and the timespan involved, that does not seem inordinate.
“It is a long time but what will be important, in my view, is to carefully scope the inquiry to see how it should be managed and to inform along the way of the progress of the inquiry and perhaps to set milestones for interim reports.”
Judge Goddard was named as chairwoman by Home Secretary Theresa May last week.
Mrs May has insisted she is confident that thorough checks have been carried out to ensure there are no conflicts of interest that could undermine her appointment.
Labour MP Keith Vaz, the committee chairman, asked Judge Goddard: “Would you regard yourself as being part of the establishment?”
She replied: “We don’t have such a thing in my country and I did have to ask carefully what is meant by it so that I did understand what I was being asked to disclose.
“My understanding is do I have any links into any institution or any person relevant to the subject matter of the inquiry? And no, I don’t.”
Judge Goddard said she arrived in the UK yesterday and had already met the Home Secretary and sex abuse survivor groups.
She told the committee she will step down from her full-time job as a judge in New Zealand and relocate to the UK for the duration of the inquiry, although she has yet to be awarded a work permit.