Victims of alleged historical sex abuse say they are going to pull out of an inquiry led by the Home Office.
The victims have sent a letter to Home Secretary Theresa May saying they have lost confidence in the investigation.
The letter states: “As survivors and associated professionals, we were very much hoping to take up the invitations to engage with your Ministerial Officers to discuss the Child Sex Abuse Inquiry, but we regret to say we have to decline.
“We, alongside many survivors, have made numerous representations to you regarding our view that the inquiry as it stands is not fit for purpose.”
Mrs May told Sky News she was aware of the letter and re-iterated that failings of parts of government and institutions must be investigated.
“The issues in the letter have been spoken about before,” she said.
“But I am clear we have a once-in-a-lifetime opportunity to get to the bottom of this issue.”
The inquiry into historical child sex abuse allegations has suffered a series of setbacks and controversies in recent months.
The first chair of the inquiry, Lady Butler-Sloss, was forced to step down due to her late brother, Lord Havers, being an attorney general during much of the period under review.
City lawyer Fiona Woolf was then appointed in September to chair the panel, but soon faced criticism over her social links to former Home Secretary Lord Brittan and his wife.
Her connection with Lord Brittancame under scrutiny as he is likely to be called to give evidence to the inquiry about his handling of child abuse allegations.
He denies failing to act on a dossier of paedophilia allegations he received while in office in the 1980s.
In late October, Mrs Woolf announced that she wouldresign from the role after victims said they did not have confidence in her.
Sky’s Jason Farrell said the victims gave three key reasons in their letter to Ms May explaining why they no longer wished to engage with the inquiry.
“They say the terms of reference go well beyond the original idea for the inquiry, namely to investigate the government and the establishment over cover-ups of paedophiles in their ranks,” he said.
“Secondly, they say that whilst the two heads of the inquiry have stood down, they also have issues around the people on the panel itself.
“The third thing that they are concerned about is that the scope for this only goes back to 1970. They feel that it should go back further.”