The 800-page report, containing details of thousands of emails and WhatsApp messages, lays bare the poisonous atmosphere within Labour between Jeremy Corbyn’s leadership team and the party’s HQ staff.
It has also put the names of party workers and whistleblowers who had complained about anti-semitism, racism and other forms of harassment into the public domain.
Supporters of Mr Corbyn claimed the report demonstrates that Labour HQ undermined efforts to combat anti-semitism in the party, and deliberately sabotaged the 2017 election campaign, which saw the party come close to denying the Conservatives power. There are scores of references to Labour staff seeking to prevent ‘trots’ from securing key positions in the party, or being elected as candidates.
In a joint statement with deputy leader Angela Rayner, Mr Starmer said the leak raised “a number of matters of serious concern”.
The Labour leader said the internal investigation would examine three areas: “First, the background and circumstances in which the report was commissioned and the process involved.
“Second, the contents and wider culture and practices referred to in the report. Third, the circumstances in which the report was put into the public domain. We have also asked for immediate sight of any legal advice the Labour Party has already received about the report.
“In the meantime, we ask everyone concerned to refrain from drawing conclusions before the investigation is complete and we will be asking the general secretary to put measures in place to protect the welfare of party members and party staff who are concerned or affected by this report.”
In a sign that the leaked report was already putting strain on party discipline, four members of Mr Starmer’s shadow frontbench team signed a statement issued by the Socialist Campaign Group of left-wing Labour MPs, calling on the party to publish the report in full.
The group also demanded an emergency meeting of the Labour national executive to discuss its contents.
“We understand the disappointment and frustration that many Labour members will feel with the details revealed in this report.
“It contains revelations of senior officials undermining the 2017 general election campaign and suggests there are cases to answer on bullying, harassment, sexism and racism.”