Labour’s ruling body will meet later to set out plans for an inquiry into a leaked document on the party’s handling of anti-Semitism allegations.
The report claimed anti-Jeremy Corbyn sentiment among Labour staff hindered efforts to tackle the issue within the party.
But others say the report was leaked in an attempt to “smear whistleblowers”.
It will be the first meeting of the National Executive Committee under the party’s new leader, Sir Keir Starmer.
He promised an independent inquiry into the contents of the report and how it was leaked after it became public over the Easter weekend.
A spokesman for Sir Keir said he wanted the investigation to be “swift” and completed within “a matter of months”.
A timetable for the inquiry is expected to be confirmed at the meeting, which is being held virtually due to the coronavirus outbreak.
Sir Keir has the support of much of the NEC and has appointed allies who will back his plans.
But he may face opposition from some – particularly those members who supported Mr Corbyn.
BBC political correspondent Iain Watson said, although the issue appeared to be an unwelcome challenge for the new leader, Labour insiders said it could provide Sir Keir with an opportunity to change both a corrosive culture in the party and, ultimately, some of its current key staff.
The report was drawn up in March 2020 – before Mr Corbyn stepped down as leader.
The 860-page document is understood to be a draft drawn up to help inform the party’s responses to an investigation by the Equality and Human Rights Commission (EHRC) into anti-Semitism within Labour.
The report said there had been “a litany of mistakes, deficiencies, and missed opportunities” to tackle the issue, and “rigorous and far-reaching reforms” had not been made soon enough.
But it also included allegations that some party staff tried to undermine Mr Corbyn’s leadership ahead of the 2017 election, along with WhatsApp messages from named individuals, appearing to make derogatory comments about Mr Corbyn, party policy and the membership.
The names were not redacted when the document was leaked to the media.
Substance and process
Many of those named in the report no longer work for the party and some are considering suing for breach of confidentiality.
And members of the GMB union branch at Labour HQ have accused the party’s general secretary – and ally of Mr Corbyn – Jennie Formby, of leaking the report. The branch passed a motion last week saying they no longer had confidence that she was making their welfare and safety a priority.
But the left-wing Socialist Campaign Group – including former frontbenchers John McDonnell and Diane Abbott – is urging members of NEC to concentrate on the substance of the allegations, rather than the process by which it was leaked.
Labour said officials were working with the Information Commissioner’s Office (ICO) over the leak and insisted it took its responsibility on data protection “extremely seriously”.