Jeremy Corbyn has been told he will have the Labour whip suspended for at least three months, as more than a dozen members of the party’s governing body attacked Keir Starmer, saying the decision “flies in the face of natural justice”. The Guardian understands that the chief whip, Nick Brown, wrote to Corbyn on Thursday night saying the whip had been withdrawn for three months – suspending him from the parliamentary Labour party – pending an investigation into whether he had broken the PLP code of conduct. Corbyn has been told the decision will be kept under review and his conduct during the suspension will be taken into account. He had been suspended from the Labour party as a whole in late October over comments he made in the wake of a report by the equalities watchdog about antisemitism in the party. He said the scale of the problem had been “dramatically overstated for political reasons” by opponents and the media. In the most open declaration of civil war in the party yet, a letter from left-aligned members of Labour’s National Executive Committee (NEC) said they expected the whip to be returned as a consequence of a decision by an NEC panel on Tuesday to give the former leader a formal warning and restore his membership to the overall party. “The decision of the leader the following day to withhold the whip from Jeremy Corbyn MP is an act of deliberate political interference in the handling of a complaint,” the letter to the general secretary, David Evans, says. “It defies the decision of the NEC panel, is a matter of double jeopardy that flies in the face of natural justice, it undermines the rule book and it is precisely the type of action found to be unlawful indirect discrimination by the Equalities and Human Rights Commission [EHRC] report.” The letter criticised Starmer’s statement that the Jewish community had no faith in the process of the NEC’s disputes panel, which it said was a “direct criticism of the decision reached by the disputes panel on Tuesday ... This criticism has been joined by that from other MPs, no doubt following the lead of the leader.” The letter said the NEC panel received legal advice on the day about the sanction given to Corbyn. “This is an unacceptable attack on the lay volunteers elected to uphold the rule book, it is direct political interference and it is unacceptable.” It said the party would now face legal action as a result of the decision and said it was “unconscionable” that NEC members should be put in this position. It called on Evans to reprimand Starmer for his actions, which it says were “intended to undermine confidence in the dispute process and for taking a decision that is directly contradictory to the NEC panel decision”. Corbyn’s lawyers have also written to Labour calling for him to be allowed back into the parliamentary party. It is understood his legal team have also made subject access requests to several key members of Starmer’s team and staff in the party’s complaints unit. The lawyers’ letter to the party questions whether procedures were properly followed when the decision not to restore the whip was taken. Starmer’s decision not to restore the whip to Corbyn following his suspension provoked a significant backlash. Earlier on Thursday, the shadow chancellor, Anneliese Dodds, blamed a “politicised” disciplinary process for Corbyn’s readmittance, the day after a former MP quit the party in protest at Starmer’s treatment of his predecessor. Thelma Walker was a former parliamentary aide to Dodds’s predecessor as shadow chancellor, John McDonnell, but lost her seat in the 2019 election. She tweeted on Wednesday: “Tonight I attended my branch meeting and resigned my membership of the Labour party. It was a privilege to serve as Labour MP for Colne Valley, to be PPS to John McDonnell and to work with Jeremy Corbyn as Labour leader. I will continue to work for the many not the few.” Dodds said the EHRC had found that Labour’s disciplinary process was not fit for purpose and should be replaced with an independent system, which the party has said it will deliver. “It’s a matter of huge regret and shame to my party that it found we were wanting. We have to sort out that system. It cannot remain as a politicised system. Keir Starmer has committed to altering it and … we are now under a statutory duty,” she told BBC Radio 4’s Today programme. Dodds said the decision to readmit Corbyn under the previous system “indicates that that process is not the right one, it’s not the one that we need … We have six weeks to respond to that report and a large element of the response is going to be around setting up a new process, which is completely independent, which everyone can have confidence in, including the Jewish community.” The MP Margaret Hodge, the parliamentary chair of the Jewish Labour Movement, who is understood to have told Starmer on Tuesday night she would resign from the party after the initial decision to readmit Corbyn, said refusing to return the whip to Corbyn “did a lot to restore his credibility”. “The terrible truth is that he [Corbyn] constantly makes himself the centre of the argument,” she told BBC Radio 4’s Today programme. “What we need to root out is antisemitism, and for as long as he is one of the individuals who refuses to accept the extent of antisemitism in the party, who constantly says that people like me have been politically motivated and are attacking him personally instead of attacking the antisemitism that he expressly tolerates, and has allowed to spread right through the party – that’s really the problem.”