The Labour Party has launched an “urgent” independent investigation into a leaked internal report into allegations of anti-Semitism in the party.

Over the weekend details emerged of an extensive internal investigation into anti-Semitism in the party carried out in the final month of Jeremy Corbyn’s time as leader.

The dossier was compiled after its authors trawled through 10,000 emails, along with thousands of private WhatsApp communications between former senior party officials, with whistleblowers who gave evidence to last year’s BBC Panorama investigation on anti-Semitism within Labour singled out for criticism.

The leaked report concluded that “factional opposition” in the upper echelons of the party towards the Islington North MP contributed to “a litany of mistakes” that hindered the effective handling of the issue.

Allies of the former leader seized on suggestions that anti-Corbyn officials worked to lose the 2017 general election in the hope that a defeat would force a change at the top.

But they were accused of using the report to “smear whistleblowers” in a bid to “discredit allegations” of anti-Semitism in the party.

Corbyn’s four-and-a-half years in charge dogged by complaints of racism against Jews and accusations senior officials were slow to crack down on members who promoted anti-Semitism.

A joint statement by new leader Keir Starmer and Angela Rayner said: “We have seen a copy of an apparently internal report about the work of the Labour Party’s governance and legal unit in relation to anti-Semitism. The content and the release of the report into the public domain raise a number of matters of serious concern.

“We will therefore commission an urgent independent investigation into this matter.

“This investigation will be instructed to look at 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.”