Campaigners have written to the directors of 20 arms manufacturers based in the UK saying they may face criminal liability for failing to prevent war crimes if their companies continue to sell military equipment to Israel. Four groups, including the Campaign Against Arms Trade (CAAT), have written to directors of arms companies that contribute parts or elements of the F-35 fighter jets used by Israel’s air force as part of the bombing of Gaza. The letter argues the company directors face a “potential criminal liability for atrocity crimes currently taking place in Gaza”, even though the UK government has continued to authorise arms sales to Israel since the start of the war with Hamas. It cites a section in the 2001 International Criminal Court Act that states it is an offence against English and Welsh law “to engage in ‘conduct ancillary’ to a war crime or a crime against humanity” in foreign jurisdictions. The company directors include those at the UK arm of Lockheed Martin, the principal manufacturer of the advanced F-35, the British arms firm BAE Systems, which makes 13-15% of each of the jets, and Northrop Grumman, a US arms maker and significant F-35 subcontractor. The other three groups behind the letter are Global Legal Action Network (GLAN), which has also brought a legal challenge against the government decision to continue arms exports to Israel, War on Want, and the International Centre of Justice for Palestinians. The campaign groups say they are willing to meet the companies to discuss the issue, but add that they are also considering filing a complaint with the Met police asking it to take action. An alternative would be to try to mount a private prosecution if the police do not respond, they added. “The Israeli military stands accused of war crimes, crimes against humanity, and genocide against Palestinians following the 7 October Hamas attacks,” their joint letter states. In it, the groups set out the legal framework governing war crimes and cite Israeli military actions they say “constitutes criminal conduct”. Israel is under growing international legal pressure over its prosecution of the war against Hamas in Gaza, now into its ninth month, amid allegations that the conduct of its offensive is at risk of becoming genocidal because of the dire humanitarian consequences faced by civilians caught up in the fighting. But Israel says it is necessary to eliminate Hamas as a military and political force in response to the violent raid on 7 October, in which nearly 1,200 Israelis were killed by attacking fighters. In the war that has followed, 37,431 Palestinians have been killed, according to the Gaza health ministry. Last month, the UN’s top court, the international court of justice, ruled Israel should halt its assault on the southern Gaza city of Rafah. However, the verdict was not binding and Israel said it would continue its offensive. A few days earlier, the chief prosecutor of the international criminal court announced he was seeking arrest warrants on war crimes charges for Israel’s prime minister, Benjamin Netanyahu, and the defence minister, Yoav Gallant, as well as three Hamas leaders in Gaza, headed by Yahya Sinwar. Dearbhla Minogue, a senior lawyer with GLAN, said individuals deemed responsible for transferring weapons to Israel were exposed to criminal liability even if the UK continued to allow arms sales to Israel. “The fact that they are hiding behind a licensing system which is unfit for purpose will not protect them if and when they face a jury of their peers, because ordinary people can see through politicians’ obfuscation,” she added.