Labour has been accused of using “secret” WhatsApp groups to interfere with the independent antisemitism inquiry, as part of testimony from 70 former staffers.
The statements form part of a submission from the Jewish Labour Movement to the Equality and Human Rights Commission (EHRC), which is due to report its findings in the new year.
Jeremy Corbyn has insisted that the party has dealt with all cases of antisemitism within the party.
However the submission made by the Jewish Voice for Labour group claims that 136 complaints were outstanding in October, while around 100 allegations were not logged in the system at all.
Speaking to the BBC’s Today programme, James Libson, a partner at the Mishcon de Reya law firm, said: “There are many, many outstanding complaints, many examples of interference and many examples of double-standards in the way in which complaints are processed.”
Asked if there was evidence that the Labour leader’s office was “interfering” in the investigations process, Libson said: “There has been interference and that interference has unfortunately become institutional.
“Institutional in the sense that people affiliated with the leader’s office – and now in the actual unit that are investigating – and that at a more basic level, information is passing between the leader’s office and investigating unit.”
This information was being passed “by USB sticks, by WhatsApp groups, secret WhatsApp groups,” he added.
Labour’s shadow housing secretary John Healey said the party had “toughened-up” its approach to tackling antisemitism.
Healey told the BBC: “Having been too slow and too weak at the start, the action being taken now has been toughened-up.
“An in-house lawyer, special appeal panels to deal with complaints, new fast-track expulsion powers that are being used.”
The EHRC has so far declined to comment.
A Labour Party spokesperson called antisemitism “evil” and said the party is cooperating with the EHRC and is “committed to rooting it out”.
“The allegation about numbers of outstanding cases is not accurate. And it is categorically untrue that anyone has been instructed to lie,” the spokesperson added.
“The Labour Party is not institutionally antisemitic and complaints relate to a small minority of our members.
“We are the only political party that has published figures on cases of antisemitism, and we regularly account for the work we are doing to tackle it.
“We have significantly reformed our procedures over the past year, including recently adopting a proposal by Jeremy Corbyn for rapid expulsions, which allows individuals to be expelled within a matter of weeks in open and shut cases.”