Labour has been accused of waging a pre-election “dirty tricks” campaign against the equalities watchdog currently investigating the party over antisemitism.

The JC has learned of growing frustration over Labour’s failure to supply “large quantities” of evidence requested by the Equality and Human Rights Commission (EHRC) to allow it to effectively carry out its probe

There are also serious concerns over the amount of redacted or edited evidence being supplied by Labour’s legal team to the investigation. Labour’s lawyers are alleged to have also refused to hand over documentation which is claimed to be “irrelevant” or “out of the remit” of the EHRC’s powers.

The EHRC confirmed to the JC on Wednesday that their investigation into claims Labour is institutionally antisemitic “will not be concluded before the end of the year”.

The JC understands that the investigation will not now be concluded until July next year at the earliest.

Labour appeared to mount an open attack on the EHRC on Tuesday when the party’s Race and Faith manifesto was launched, containing a commitment to make the organisation “truly independent” if in government.

A BBC Newsnight report on Tuesday evening, which questioned the independence of two senior figures within the EHRC, coincided with Labour’s attack on the EHRC.

Last week Peter Mason, national secretary of the Jewish Labour Movement, (JLM) confirmed that his organisation had only just sent its own submission to the watchdog containing “thousands” of examples of unresolved antisemitism.

On Wednesday, when asked to comment on Labour’s attempt to frustrate the EHRC investigation a JLM spokesperson said: “The Labour Party is up to dirty tricks with the EHRC.

"Refusing to cooperate and skirt around the EHRC’s requirements is not engaging in good faith with the investigation which is what Labour have publicly stated they would do.”

One insider said Labour’s tactics appear to be designed to “frustrate, stifle and slow down” the speed of the watchdog’s investigation into the party.

An EHRC source said: “Labour’s lawyers know all the tricks of the trade regarding the disclosure of evidence.

“It is extremely frustrating when one considers the huge amount of documentary evidence that must exist and is being kept from us.

‘’We don’t have powers to raid offices or people’s homes. This whole process requires us to rely on the bona fides of those we investigate.’’

The source added: ‘’It is a matter of huge concern that so much trust is being placed in officials and employees to decide relevance or admissibility. The lawyers have a duty to use their best endeavours to ensure that everything is produced.

‘’Redactions or edited documentation slow down the whole process as it becomes necessary to query whether or not these have been made on the advice of the lawyers or whether a free hand is given to those being investigated.’’

Dozens of Labour Party staff have now been sent letters compelling them to submit evidence to the EHRC over how they dealt with complaints about antisemitism with the party.

Amongst those asked to give evidence are lay members of the NEC. But it is understood that the investigation will not include requests for Mr Corbyn or any other senior party official to cooperate with the probe.

The source admitted: “Transparency is a critical part of the investigation. If officials are being kept in the dark, one must question why that is happening and how much is thus being kept from us.’’

Labour submitted their initial response to the EHRC earlier in the summer - but the details remain a closely guarded secret.

Former deputy leader Tom Watson publicly complained that he, along with other members of the party’s ruling NEC, had not been shown this response prior to it being sent. Mr Watson said he was “very concerned” that he and other members of the Labour NEC were given access to the party’s response.

“I’ve been told by a general secretary that I’m not legally responsible for dealing with outside regulatory bodies,” Mr Watson said.

The Labour Deputy Leader had also previously said he was “deeply concerned” by whistleblower allegations that emails from Labour’s general secretary, Jennie Formby, about investigations into antisemitism claims were deleted, after he had been assured by Ms Formby they had been preserved.

Anger mounted this week after Labour questioned the independence of the EHRC at Tuesday’s launch of its Race and Faith manifesto.  The manifesto claimed that if elected the party will “enhance the powers and functions” of the EHRC “making it truly independent.”

Labour sources insisted the pledge was a repeat of something that appeared in the party’s 2017 election manifesto – but including the pledge in the new manifesto was viewed as a provocative gesture towards the watchdog while it was carrying out its investigation into the party.

Sources have told the JC that Labour hoped that a report by BBC Newsnight on Tuesday evening, which aimed to question the independence of the EHRC chair David Isaac, would add to suggestions that the organisation lacked independence.

The report by Newsnight’s political editor Nicholas Watt suggested concerns had been raised within the EHRC over Mr Isaac’s reluctance to take public positions on issues such as Shamima Begum, the former east London schoolgirl who fled to UK to join Isis in Syria, but is now seeking to return.

Newsnight also suggested that Rebecca Hilsenrath, the EHRC’s chief executive, had expressed concern about Labour’s antisemitism herself in 2017, well before the probe into Mr Corbyn’s party was launched. 

But Labour’s hopes of escalating concern over the independence of the EHRC were shattered by Mr Corbyn’s performance during an interview with Andrew Neil on BBC1 on Tuesday evening.

Trevor Phillips, the former chair of the EHRC, also played down the issue, telling Newsnight that claims that the watchdog was not independent were no new. He said that he realised being head of the EHRC would win you “no friends”. 

Mr Phillips also revealed that when the EHRC conducted its probe into the far-right British National Party in 2010,  “Labour ministers” had been amongst those to say it was “not the Commission’s business” to investigate a political party.

A spokesperson for the Equality and Human Rights Commission, told the JC on Wednesday: “Our investigation is ongoing and will not be concluded before the end of the year. We cannot give any further indication of a timeframe.”

A Labour spokesperson denied documents had been redacted and said the party were being advised by one law firm.

The spokesperson added:”We are fully cooperating with the EHRC and sharing evidence."

A spokesperson from the EHRC said: “The alleged source making these comments was not speaking from an informed position nor with authority about this investigation.”