The equalities watchdog has launched a formal investgiation into Labour over allegations it "unlawfully discriminated against, harassed or victimised" Jewish people.

The step makes Labour only the second political party to face such a probe by the Equality and Human Rights Commission (EHRC). The first was the BNP.

The EHRC had previously launched a preliminary investigation after it received a dossier of Jew-hate by members from the Jewish Labour Movement (JLM) and the Campaign Against Antisemitism (CAA). The party's response failed to dissaude it from opening a wider investigation.

On Tuesday, an EHRC spokesperson said it was "launching a formal investigation to determine whether The Labour Party has unlawfully discriminated against, harassed or victimised people because they are Jewish".

They added: "The EHRC is pleased that The Labour Party has committed to co-operate fully with its investigation.

"The EHRC has carefully considered the response it has received from the Party and has now opened a formal investigation under section 20 of the Equality Act 2006 to further examine the concerns.

"The investigation will seek to determine whether unlawful acts have been committed by the party and/or its employees and/or its agents; and whether the Party has responded to complaints of unlawful acts in a lawful, efficient and effective manner.”

Its investigation will look into whether "unlawful acts" were committed and whether the party "responded to complaints of unlawful acts in a lawful, efficient and effective manner".

JLM chair Mike Katz said: "For years we have been warning that the Labour Party’s response to antisemitism within our ranks has been woeful at best, and institutionally racist at worst.

"Last year we took the unprecedented step to refer the party to the EHRC, and we welcome their decision today to launch a full statutory inquiry. "

"Labour has repeatedly failed to address its own antisemitism problem," said CAA chairman Gideon Falter.

"When the Commission approached the Labour leadership, they still failed to offer to action sufficient to reassure the Commission that the antisemitic discrimination and victimisation would stop...

"In just four chilling years, Jeremy Corbyn has turned the Party which pioneered anti-racism into the Party that now finds itself in the company of the BNP, being investigated by the very equality and human rights regulator it once fought so hard to establish."

Board of Deputies President Marie van der Zyl weclomed the probe.

She said: "We note that the last party to face a racism probe from the EHRC was the British National Party, which is a truly shameful indictment.

"In the past four years we have seen a large number of cases of antisemitism throughout the party from bottom to top. Despite the Jewish community demonstrating in their thousands outside Parliament, this has still not been addressed seriously by the party leadership.

"We will await with interest the EHRC report into racism at the heart of the UK’s official Opposition.”

Labour issued a statement in response defending itself but also attacking the large budget cuts EHRC, which it founded while in Government, suffered since it left office.

"Labour is fully committed to the support, defence and celebration of the Jewish community and is implacably opposed to antisemitism in any form," a spokesperson said.

“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.

"We support the efforts of the EHRC to draw attention to the obligations all political parties have under the Equality Act. But its ability to do so has been undermined by a 70 per cent budget cut since 2010.

"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.”

Barrister Adam Wagner, who is acting for CAA, said the probe could take more than a year, adding the decision to investigate "shows how serious the issue is".

"This is also a sad day for the Jewish community and Labour Party. It should not have come to this," he said.