The new Labour leader, Sir Keir Starmer, has ordered an immediate review into a leaked internal report into antisemitism in the party which concluded that factional hostility to his predecessor, Jeremy Corbyn, hampered efforts to tackle the problem.

Starmer and his deputy, Angela Rayner, said on Monday that an independent investigation would examine the leaking of the 860-page document, details of which emerged over the weekend, as well as its contents including the “wider culture and practices” it refers to and the “background and circumstances in which the report was commissioned and the process involved”.

The report uncovered many failings in the process for tackling antisemitism complaints before Jennie Formby, the current general secretary, took over in 2018. It said there was an “abundant evidence of a hyper-factional atmosphere prevailing in party HQ in this period, which appears to have affected the expeditious and resolute handling of disciplinary complaints”.

It was intended to be submitted as an annex to the Equalities and Human Rights Commission inquiry into Labour’s approach to dealing with antisemitism. It is understood that it will now not be submitted.

The report was completed this year in the last months of Corbyn’s leadership and its conclusions clash with complaints of whistleblowers, formerly working for Labour, who told BBC Panorama last year there had been political interference in the process from the top of the party under Corbyn.

The report, seen by the Guardian, says it found no evidence of antisemitism complaints being treated differently from other forms of complaint, or of current or former staff being “motivated by antisemitic intent”.

“We have also asked for immediate sight of any legal advice the Labour party has already received about the report,” Starmer and Rayner said in a statement.

“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.”

The previous Labour leadership’s handling of allegations of antisemitism against party members overshadowed parts of the 2019 general election campaign. During a high-profile televised interview with Andrew Neil, Corbyn repeatedly declined to apologise to the British Jewish community for the way his party had handled complaints.