An 82-year-old Jewish woman, who is being investigated by Labour for alleged antisemitism for the third time in less than three years, is threatening legal action against the party, claiming it has unlawfully discriminated against her based on her belief in anti-Zionism. Diana Neslen, who lives in east London, regularly attends her local synagogue and keeps a kosher home but has been accused of antisemitism for tweets she has posted about Israel and Zionism. In a pre-action letter to Labour, her lawyers, Bindmans, say the party’s investigation is totally unjustified and disproportionate as it rests on a single tweet from 2017, which said “the existence of the state of Israel is a racist endeavour and I am an antiracist Jew”. They claim anti-Zionism is a protected philosophical belief under the Equality Act and Neslen has been “subjected by the party to discrimination and harassment related to her protected philosophical belief”. Neslen, who said she was a “committed Zionist” before she visited Israel, told the Guardian: “I remember thinking at the end of the war, ‘Why didn’t the Germans do anything?’ When there’s injustice done in your name you cannot close your eyes to it. That’s why I feel very strongly. “The Labour party has no idea in my opinion of what antisemitism is. My son was attacked by a luminary of the BNP [British National party] who was jailed for three years. I remember picking up the phone and being subjected to death threats from the BNP. People who have never experienced antisemitism have no idea what it means, what it means for a Jew to be found guilty of antisemitism.” Neslen, who grew up in South Africa, said she had spent her life fighting apartheid and racism. In 2018, while mourning the death of her husband of 51 years and having recently been diagnosed with cancer, she was sent a “reminder of conduct” accusing her of antisemitic comments on social media. In February this year, she was given a “formal NEC warning relating to your conduct”. Bindmans said all bar one of the tweets cited in the latest investigation, of which she was notified in August, were excluded under party rules either because they were before she rejoined the party in 2015 or were considered in the previous investigation. In 2018, Labour, beset by antisemitism allegations, adopted the International Holocaust Remembrance Alliance’s definition of antisemitism, which includes as an example: “Denying the Jewish people their right to self-determination, eg by claiming that the existence of a state of Israel is a racist endeavour.” Neslen is a member of Jewish Voice for Labour, which says it knows of 42 Jewish members of the Labour party, two of whom have since died, who have faced or are facing disciplinary charges relating to allegations of antisemitism. The group estimates that Jewish Labour party members are at least five times more likely to have faced actioned complaints of antisemitism than non-Jewish members. The letter from Bindmans quotes the judge who, in the case of Maya Forstater earlier this year, determined that gender-critical views were a protected philosophical belief, saying “only if the belief involves a very grave violation of the rights of others, tantamount to the destruction of those rights, would it be one that was not worthy of respect in a democratic society”. Neslen is threatening to sue Labour if it does not apologise and undertake not to pursue further investigations against her in respect of her beliefs. Labour has not replied to letters from her lawyers and did not respond to a request for comment from the Guardian.