Allegations of bullying and sexual assault at the headquarters of the national child abuse inquiry have not been taken seriously enough and the inquiry's response to these claims has been "inadequate", a Commons report has claimed.
A catalogue of problems has "seriously diminished" confidence in the Independent Inquiry into Child Sexual Abuse (IICSA) and its ability to deliver on objectives in a "timely and effective way", MPs warned.
The Home Affairs Committee pointed out that experienced counsel have been departing from the probe at an "alarming rate".
Ben Emmerson QC, the most senior lawyer appointed to the inquiry resigned in September, following an allegation he had sexually assaulted a female "inquiry worker" in the lift at its offices. Mr Emmerson strenuously denied the claim.
The alleged victim gave an account of the incident on the day it happened, but did not want the incident to be investigated, it was reported.
However, MPs said the inquiry has reportedly denied receiving any complaint.
Mr Emmerson also categorically denied bullying or any other misconduct.
The committee's report said: "It is not for us to pass any comment on the allegations made in the media about the former counsel to the inquiry, which he has categorically denied.
"We are not in a position, and it is certainly not our responsibility, to assess either the facts of the case or the details of the processes that the inquiry pursued.
"However, on the basis of the evidence we have seen, we do not believe that IICSA has taken seriously enough its responsibility to pursue allegations of bullying or disclosures of sexual assault within the inquiry.
"Nor do we believe it has done enough to demonstrate publicly that it has a robust approach to such matters."
The report also said the appointment of a new legal lead counsel should be a "priority" for the inquiry, and that it was "concerned" one had not yet been chosen.
The probe - described as the most ambitious public inquiry ever launched in England and Wales - has been plagued by problems since it was set up by then home secretary Theresa May in 2014, and there are suggestions it could cost more than £100 million.
In the latest setback, last week one of thelargest victims' groups involved withdrew from the probe, branding it an "unpalatable circus".
The development sparked calls for chairwoman Professor Alexis Jay to be replaced - but she has been backed by the Government.
Labour MP Yvette Cooper, chair of the committee, said: "This Inquiry is far too important to be sunk by problems. That's why urgent action is needed to sort them out. Survivors of abuse deserve nothing less."
Prof Jay - the fourth person to lead the inquiry - announced that it will invite an external senior legal figure to review some of the issues raised in the committee's report.
"While I am confident that our safeguarding and dignity at work procedures are robust, I recognise the impact of recent speculation and commentary about them," she said.
The former senior social worker said: "Nobody is more determined to deliver a successful inquiry on behalf of victims, survivors and the wider public than the panel and myself.
"We recognise that the past few months have been difficult for the inquiry and for the victims and survivors who have placed their trust in it.
"I am personally sorry for any unnecessary anxiety the inquiry may have caused to victims and survivors during this transitional period."
She will publish a review of how the inquiry operates in the coming weeks.
"While this will not alter our terms of reference, I believe it will make the work of the inquiry more transparent and set out a clear path for how the inquiry will progress," Prof Jay said.
The report also criticised the inquiry's former chair, Dame Lowell Goddard, accusing her of refusing to provide oral evidence to the committee, something it described as "disgraceful" and falling “well below the standards we would expect of any public servant".
However, earlier this month, the former New Zealand High Court judge said she had never declined to provide oral evidence to the committee.
The Home Secretary and Permanent Secretary's failure to provide the committee with "full and early information" on the reasons behind Dame Lowell's early departure were also branded "regrettable".
Elsewhere, delays in starting public hearings and engaging with survivors were called a "weakness", by the MPs, who added the issue "must be addressed in Professor Jay’s review if IICSA is to build the confidence of survivors and maintain their engagement with its work".
The committee added they "look forward" to the conclusion of the review by Prof Jay, but noted "the tension identified by Dame Lowell Goddard between a judicial-style approach to the Inquiry’s work and an inspectorate-style approach", suggesting the inquiry could split into two strands to make its "work more manageable and ultimately effective".
Home Secretary Amber Rudd said the inquiry "has a vital role to play in exposing the failure of public bodies and other major organisations to prevent child sexual abuse".
She added: "I am confident of the inquiry's ability to confront the appalling reality of this abuse and my department is absolutely committed to supporting it in doing so.
"We owe it to victims and survivors to get this right."