Labour is under investigation by the Equalities and Human Rights Commission – making it the second party to be probed by the watchdog after the British National Party.
In a statement, the watchdog confirmed Labour has committed to co-operate fully with its investigation.
The EHRC says it is opening an investigation into Labour under section 20 of the Equality Act 2006 after preliminary research carried out since March.
The probe will determine whether the party, its employees or its “agents” unlawfully discriminated against, harassed or victimised Jews.
Under the investigation, the EHRC will have full statutory powers to demand access to documents, emails, WhatsApp messages and witnesses as part of the investigation.
The announcement follows legal complaints made by Campaign Against Antisemitism and the Jewish Labour Movement.
Gideon Falter, chief executive of Campaign Against Antisemitism, said: “We are pleased that the commission’s terms of reference closely follow our recommendations and will see a root and branch investigation of the Labour Party’s antisemitic discrimination, victimisation and harassment, as well as how the Party’s processes and decisions contributed.
“We commend the commission for acting on our referral and we have full confidence in its resolve to investigate thoroughly and deliver justice.”
A Labour Party spokesperson said: “Labour is fully committed to the support, defence and celebration of the Jewish community and is implacably opposed to antisemitism in any form.
“We reject any suggestion that the Party does not handle antisemitism complaints fairly and robustly or that the Party has acted unlawfully, and we will continue to cooperate fully with the EHRC.
“There has been a deeply worrying rise in antisemitism in the UK and across Europe. We are taking action to root it out of our party by strengthening our rules and procedures.
“But the issue can only be properly dealt with by all political parties working together to protect the interests of the Jewish community and to combat racism in politics, the media and in society more broadly.
“That includes the need for the Conservatives and other parties taking action to deal with racism in their own ranks.”