Keir Starmer has launched an “urgent investigation” into a leaked internal report documenting behaviour by Labour officials and its effect on how the party dealt with complaints about antisemitism.

The document, commissioned up in the last days of Jeremy Corbyn’s leadership, says that factionalism by officials associated with Labour’s right wing made it harder to deal with the issue of anti-Jewish racism.

A massive cache of leaked WhatsApp messages and emails detailed in the 860 page report also suggest that anti-Corbyn officials worked to lose the 2017 general election in the hope that that a defeat would force a change of leader – a revelation which has sparked anger among MPs and members.

In a joint statement with his deputy Angela Rayner, Sir Keir said the investigation would look at the circumstances the report was commissioned in, the “wider culture and practices referred to in the report” and also look at how the document was leaked into the public domain.

“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 antisemitism. The content and the release of the report into the public domain raise a number of matters of serious concern,” the statement said.

“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.”

An independent investigator is expected to be announced to lead the inquiry in due course.

Tactics by anti-Corbyn staff evidenced in the report include channelling resources to candidates associated with the right wing of the party, refusing to share information with the leader’s office, as well as “coming into the office and doing nothing for a few months” during the election campaign.

It also documents abusive discussions about colleagues and members on the left of the party.

The Socialist Campaign Group, which represents dozens of MPs on the left of the party, said in a statement on Monday afternoon that the report should be published in full and that an emergency NEC meeting should be held to discuss its contents and the terms of the investigation.

The content and the release of the report into the public domain raise a number of matters of serious concern Keir Starmer and Angela Rayner

“We understand the disappointment and frustration that many Labour members will feel with the details revealed in this report,” the group said.

“It contains revelation of senior officials undermining the 2017 general election campaign and suggests there are cases to answer on bullying, harassment, sexism and racism.

“We express our solidarity with Labour volunteers who give up their spare time to fight for a better society and get a Labour government.”

It also called on socialists to “stay and fight for a Labour government” rather than leave the party. The signatories of the statement include four members of Sir Keir’s front bench: Dan Carden, Imran Hussain, and Rachael Maskell, Lloyd Russell-Moyle.

Momentum, a group which organises members on the left wing of the Labour party, said the inquiry should, include an investigation into “the possible misuse of funds” by officials.

Sky News, which first reported the existence of the dossier, reports that Labour party lawyers have decided against sending it to the Equality and Human Rights Commission, which is currently holding an investigation into antisemitism in the party. It is understood that the report may have been drawn up to help the party understand how its own disciplinary processes operated in recent years and not intended for submission to the EHRC.

Protests against Labour antisemitism Show all 14 1 /14 Protests against Labour antisemitism Protests against Labour antisemitism Protesters clashed during the demonstration Reuters Protests against Labour antisemitism Members of the Jewish community hold a protest against Labour party leader Jeremy Corbyn and antisemitism in the Labour Party AFP/Getty Protests against Labour antisemitism Protesters hold placards and flags during a demonstration, organised by the British Board of Jewish Deputies for those who oppose antisemitism, in Parliament Square Reuters Protests against Labour antisemitism Hundreds of people gathered in Parliament Square to protest against antisemitism in the Labour Party EPA Protests against Labour antisemitism Labour MP Luciana Berger speaks during the protest PA Protests against Labour antisemitism A protester blows through a shofar during the demonstration Getty Protests against Labour antisemitism Members of London's Jewish community protest in support of Labour leader Jeremy Corbyn outside parliament EPA Protests against Labour antisemitism Labour MP John Mann speaks during a protest against antisemitism PA Protests against Labour antisemitism People protest against antisemitism in the Labour Party as Jewish community leaders have launched a scathing attack on Jeremy Corbyn, claiming he has sided with antisemites ‘again and again’ PA Protests against Labour antisemitism Labour politicians Stella Creasy and Chuka Umunna leave after attending the demonstration Getty Protests against Labour antisemitism A pro-Jeremy Corbyn protester holds a placard during a counter-protest Getty Protests against Labour antisemitism A support of the Labour Party hold up a placard during the demonstration Reuters Protests against Labour antisemitism Jeremy Corbyn supporters during the demo Reuters Protests against Labour antisemitism A protester holds up a sign reading ‘For the many, not the Jew’ AFP

Labour was put under investigation by the EHRC after the body received a number of complaints about the party’s response to complaints about antisemitism. The party has moved to expel members accused of anti-Jewish racism, but has been accused by critics of not doing so fast enough or making the wrong decisions in some cases. Critics of Mr Corbyn say his politics, and particularly his support for Palestinian liberation, has attracted antisemities to the party – though the Home Affairs Select Committee found “no reliable, empirical evidence to support the notion that there is a higher prevalence of antisemitic attitudes within the Labour Party than any other political party”.