Labour’s most senior lawyer under Jeremy Corbyn formally warned the party that an internal report on antisemitism was deliberately misleading and relied upon improperly obtained private correspondence, leaked documents show. Thomas Gardiner, Labour’s director of governance and legal until last month, wrote that the report should not be circulated because party employees’ emails and WhatsApp messages had been “presented selectively and without their true context in order to give a misleading picture”. The report, which was leaked to the media, was compiled to be submitted to an inquiry by the Equalities and Human Rights Commission (EHRC) into Labour’s handling of antisemitism complaints. Gardiner’s comments, sent in an email to the party’s then general secretary, Jennie Formby, will be a key piece of evidence for 32 former Labour officials, including the former general secretary Iain McNicol, who are suing the party for data breaches and libel within the leaked report. The 851-page report – which is subject to an independent inquiry led by QC Martin Forde – blames former Labour officials opposed to Corbyn for hampering his efforts to tackle abuse and sabotaging the party’s 2017 general election campaign. The report included WhatsApp messages, emails and texts from staff. Formby told the Guardian she authorised the search of the party’s internal systems, including WhatsApp groups, after the EHRC asked her to do so for its inquiry. Supporters of the current Labour leader, Keir Starmer, have accused Corbyn and his allies of unleashing a wave of claims against Labour that threaten to leave the party having to pay hundreds of thousands of pounds in legal bills. Allies of Corbyn have hit back, saying Gardiner had previously supported publication of the report and the use of private correspondence but had changed his mind after becoming aware it had been leaked to the media. According to documents seen by the Guardian, Gardiner wrote the email to Formby to register his concerns on 11 April. He objected that the authors were trying to “lay false blame” on him for failings in the complaints process. He continued: “I also object further on the grounds that large sections of the report have been compiled using email searches which were not authorised for the authors to undertake including improper searches of my email account. “The report also includes confidential private WhatsApp and other messages – a clear and unacceptable breach of confidence. Further, these messages are presented selectively and without their true context in order to give a misleading picture,” he wrote. “I realise it will not be helpful not to further use the report, given that it has apparently been leaked in a previous version, but I must register this formal objection.” Formby told the Guardian she had authorised the searches of emails and WhatApp messages, which were legitimately carried out at the request of the EHRC. “As general secretary, I authorised the searches which were legitimately carried out. The information used in the internal report into the handling of antisemitism complaints came to light when searches were undertaken in response to EHRC requests,” she said. “The EHRC asked the Labour party to search all its internal systems, including WhatsApp groups where possible, and the party’s staff handbook makes clear that staff communications on internal party systems can be searched in this way.” One of the 32 claimants told the Guardian the evidence in Gardiner’s email was “hugely damaging” for Labour. “Those looking to take legal action against [the] party for the leaked report have long argued that the messages have been edited to create a misleading and damaging impression. What this email suggests is that this is exactly what Labour knew it was doing,” the claimant said. The email was revealed amid renewed Labour infighting after the party agreed to pay out a six-figure sum to seven former employees and a BBC journalist, admitting it defamed them in the aftermath of a Panorama investigation into its handling of antisemitism. The leaked report was intended to be submitted as an annexe to the EHRC inquiry into Labour’s approach to dealing with antisemitism. Commissioned before Starmer became leader, it contained leaked WhatsApp messages referring to Corbyn-supporting party staff as “trots” and conversations referring to the former director of communications Seumas Milne as “dracula”. There were also mentions of Corbyn’s former chief of staff, Karie Murphy, as “medusa”, a “crazy woman” and a “bitch face cow” that would “make a good dartboard”. Formby, who stood down as general secretary in May, declined to comment on Gardiner’s email. “In view of the ongoing independent inquiry it would not be appropriate,” she said. A Labour party spokesperson said: “It would not be appropriate to comment further while investigations are being carried out.” The EHRC said: “This is still an ongoing investigation and we cannot comment on the details.” Gardiner, who stood down as head of the governance and legal unit in June, was also approached for a comment.