Simon Bass is urging the Home Secretary to listen to abuse victims when choosing the chairperson.
It's after Fiona Woolf became the second chairperson to stand down because of alleged links to the establishment she was meant to be investigating.
Home Secretary Theresa May will make a statement to Parliament on Monday about how the inquiry will proceed.
Simon Bass told Premier he hoped she wouldn't make a rush decision.
He said: "It is so necessary to not do any knee-jerk reaction and appoint somebody tomorrow but instead look at what wants to be achieved and who would be best placed to head up such an inquiry."
The inquiry, set up by ministers in the wake of the Jimmy Savile scandal, will look at whether public bodies and other institutions, including the Church, did enough to protect children from sexual abuse, from 1970 to the present day.
Simon Bass added: "The important thing is that whilst understanding that somebody with a legal brain is helpful to have heading the enquiry it must be somebody that everyone, particularly survivors, have confidence in."