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The abuse of children has left "permanent scars on the victims and on society," Justice Lowell Goddard said as she opened the independent inquiry into the matter.
The high court judge said "no one, no matter how powerful" they were would obstruct her investigation.
She added: "No one will have immunity from scrutiny by virtue of their position.
"The task ahead of us is daunting. We must difficult questions to politicians, faith leaders, headteachers, police officers and public officials of all kinds, and we will carry on putting those questions until we get the answers."
Goddard also said:
- The inquiry will focus on England and Wales and further afield if relevant
- All victims will be anonymised and not made to feel like they are on trial
- A victim advisory board has been appointed to provide specialist advice
- Immunity from prosecution will be offered to ex-public servants who testify but not if they admit taking part in child abuse
- The inquiry is expected to last five years but has "no cut off" and regular reports and recommendations on its findings will be published
The inquiry into allegations of child sex abuse by a VIP paedophile ring will cost millions and probably will not finish within five years, a Labour MP has warned.
Keith Vaz, who chairs the Home Affairs Select Committee, told BBC's Victoria Derbyshire show it "could take up to 10 years".
Already the inquiry has cost £1.2 million before it has even begun, which equates to just under £5,000 a day.
A team of trained counsellors will operate a free dedicated helpline run by the NSPCC for those wishing to give evidence to the Goddard inquiry.
NSPCC chief executive Peter Wanless, said: "Many victims of abuse have been waiting too long for an opportunity to speak out and get justice.
"Many of them will have harrowing stories to tell so we want to make what could be a tortuous journey as easy as possible.
"Our counsellors have vast experience of dealing with sensitive issues so the dedicated helpline will be a vital part of the inquiry's work."
The helpline number is 0800 917 1000.
Labour MP Tom Watson has warned that an independent inquiry opening today will have to deal with an "epidemic" of historical child sex abuse.
Watson, who first called for investigations into an alleged Westminster paedophile ring in 2012, said the inquiry must "meticulously" investigate "failures" that contributed to the alleged abuse - not just in public services and child protection systems but also other institutions.
The inquiry will open today in Westminster, with chair Justice Lowell Goddard outlining how evidence will be taken, timescales and areas of public life that will be examined.
Victims' representatives have complained about delays to the launch of the inquiry, which followed the resignations of two previous chairs, Baroness Butler-Sloss and Fiona Woolf.
While some have expressed their lack of confidence in the inquiry, Phil Shiner of Public Interest Lawyers - which is acting for a number of survivors - said its importance "cannot be underestimated".
Latest ITV News reports
An major independent inquiry into historical child sexual abuse will launch today after a series of delays and leadership issues.