A victim group has said it is formally withdrawing from the national inquiry into child sexual abuse, claiming the investigation is "not fit for purpose".
Survivors of Organised and Institutional Abuse (SOIA) said it announced the decision with "deep regret" but felt the probe was not serving the needs of victims.
The group said survivors have been "totally marginalised" from the process, adding that the inquiry had descended into a "very costly academic report writing and literature review exercise".
It comes after the Shirley Oaks Survivors Association (Sosa) - one of the largest victims' groups involved - pulled out of the Independent Inquiry into Child Sexual Abuse (IICSA), describing it as a "stage-managed event" which has "lurched from crisis to crisis".
SOIA, part of the national WhiteFlowers survivor and whistleblower campaign, said in a statement: "It is with deep regret that SOIA announces its withdrawal from the inquiry.
"We emphasise that each of us will continue to vigorously campaign outside of the IICSA , for the rights of survivors of organised and institutional abuse to justice and healing."
SOIA, which had four core participants involved in the process, said it supported the concerns aired by Sosa in November.
It added: "We wish to thank all those who have contributed time, effort and their own money to WhiteFlowers and SOIA.
"However, we believe that, despite our efforts, IICSA remains not fit for purpose.
"Indeed it has descended into a very costly academic report writing and literature review exercise with survivors totally marginalised from effective participation in the research process."
More than 200 victims and survivors are involved in the inquiry, which has been plagued by controversy since it was launched by then home secretary Theresa May in 2014.
An IICSA spokeswoman said: "Whilst we regret the decision by SOIA to withdraw from the inquiry, we would like to reassure all victims and survivors that the important work of the inquiry continues.
"The inquiry would welcome SOIA or any of its individual members back should they decide to play a formal role in the inquiry again.
"We have taken on board a number of issues raised by SOIA and other groups over the last few months.
"We have done so wherever possible within the legal framework of a fair process and the provisions of the Inquiries Act 2005.
"Over 200 individual victims and survivors are core participants to the inquiry as well as a number of other survivor groups and institutions.
"Victims and survivors may also participate and contribute to the work of the inquiry through events including forums, research seminars and participation in the Truth Project."