Speakers included Chief Rabbi Ephraim Mirvis and Maajid Nawaz, co-founder of counter-extremism think tank Quilliam, who is a Muslim.
Douglas Murray, associate director of the Henry Jackson Society, said "We have to stop the lies." He said it had become "acceptable discourse for people to say that Israel is committing a 'genocide' instead of the most targeted military campaign against a terrorist group in history."
Thousands of people have taken part in anti-Israel protests in recent weeks accompanied by antisemitic violence. Pro-Palestinian rioters vandalised a Tesco store in Birmingham over a refusal to boycott Israeli products. Demonstrators rioted outside a Kedem store in Manchester. Dozens of death threats were made to the store's owners.
Hate crimes against Jews have risen 383 per cent worldwide since 2013, and 436 per cent in Europe. According to a Jewish newspaper, nearly two-thirds of the UK's Jewish population have questioned their future in the UK.