It has emerged that Len McCluskey’s Unite union is paying the legal fees of five people accused of leaking  a pro-Corbyn dossier on Labour antisemitism. 

The case is being brought by Emilie Oldknow, Labour’s former director of governance, who is  attempting to force the party to reveal the identities of those who leaked the report, which sought to exculpate Jeremy Corbyn over the crisis and contained hundreds of private messages.

Ms Oldknow, who is bringing claims for defamation and misuse of private information, demanded in a hearing in the High Court that the names of the leakers be revealed so she could sue them.

The move, known as a Norwich Pharmacal Order, was exclusively revealed by the JC last week, and has previously been used against social media companies such as Twitter to get them supply the names of anonymous users.

Labour’s legal representative said it was ready to disclose its internal evidence to allow the leakers to be identified, but the party has said it wanted to remain neutral and did not wish to offer “subjective opinion on who is legally liable”.

On Monday the five unnamed individuals, who have denied being behind the leak, also attempted to present their case at the same hearing.

Their barrister, Jacob Dean, confirmed to the judge that the five’s legal representation with the firm Carter Ruck was being funded by Len McCluskey’s Unite union.

Ms Oldknow is bringing claims for defamation and misuse of private information over the leaking of the report, which contains more than 500 references to her.

After the report was  leaked to the media without redaction last April,  details of staffers’ private conversations expressing hostility towards  Mr Corbyn featured among its 860 pages.

Also in the report were details of confidential complaints relating to antisemitism from Jewish members of the party and from non-members.

The apparent data breaches have led to scores of legal cases being mounted against the party, as well as the now delayed Forde Inquiry and an investigation by the Information Commissioner’s Office (ICO).

Representing the Labour official  William Bennett QC told the court on Monday that the report was a “politically-motivated hatchet job” which sought to blame Ms Oldknow and others for Labour’s “failure” to deal with allegations of antisemitism.

He said the party decided the report “could not be submitted to the Equality and Human Rights Commission because it was deliberately misleading and relied on improperly obtained private correspondence”.

He told the court Ms Oldknow “wishes to bring those people to account, who anonymously, surreptitiously leaked the Labour Party report against the wishes of the Labour Party”.

Mr Bennett said in written submissions that Labour has “reached a clear view as to who was responsible for the leak”, but has “studiously avoided giving any explanation as to what happened”.

He said Ms Oldknow has “a strong case” to bring claims for defamation and misuse of private information against those who leaked the report.

But she “needs to know which wrongdoer played what role and whether there is a viable case against some or all of them”, Mr Bennett said.

Anya Proops QC, representing the Labour Party, admitted  the leaked report “contained extensive quantities of personal data relating to a wide number of individuals, including Ms Oldknow” and was “highly confidential.”

But she  said the party has concluded that “it did not authorise the leak and it is innocent of any responsibility”.

Speaking  on behalf of the five unnamed individuals, Jacob Dean QC said: “They have cooperated fully with the various investigations into that leak, providing detailed personal, private and confidential information to those investigations, on assurances of confidentiality.”

He added that “the potential for injustice is manifest” if Labour was forced to “disclose a mass of evidence… from which the (party) has drawn certain conclusions in order to allow the applicant to draw her own, possibly different, conclusions”.

But after an hour of trying to make arguments in application hearing, Mrs Justice Tipples that the five individuals had no role in this particular case.

Labour asked for the case to be adjourned for a week.

A Unite spokesman said: “Unite offers all of our members representation in respect of employment matters.

“This court application is seeking to ask Labour to identify five members of Unite, all of whom deny leaking of the report but who participated in good faith with the Labour Party investigation on the understanding the investigation would be confidential and protect their rights to privacy.”

They added: “Today's application was a balance between the privacy rights of employees, for whom the employer has a responsibility, and the rights of Emilie Oldknow and others who are named in the leaked report.

“As to be expected, Unite has sought to represent the interests of our members and is disappointed that the court has ruled we cannot be a party to the proceedings. Upholding the employment rights of all of our members is central to Unite's core values.”