At least 330 Labour councillors have signed a letter urging Keir Starmer to back a ceasefire in Gaza, despite the Labour leader’s attempts to reassure the party over the issue. The councillors, two-thirds of whom the Guardian understands are not Muslim, have criticised the party’s refusal to back the policy, which they say is “harming communities across the UK”. Starmer detailed his position on the crisis on Tuesday after mounting criticism from MPs over his stance on the suffering of Palestinians. But the councillors have urged him to go further and “unequivocally condemn” all acts of violence against civilians. “As community leaders, we are proactively supporting our residents by speaking to faith and community groups and working to protect our communities who are facing rising hate crime and racially motivated violence,” the letter says. “The intensified human catastrophe in Gaza impacts us all, and the Labour party’s failure to call for an end to violence is causing hurt in our communities.” Reacting to Starmer’s speech, one Labour official formerly critical of Starmer’s stance said the speech had done enough to keep the party together in the short term. “We can stand by this position,” they said. “The main thing is to look like we care about Palestinian lives rather than arguing about the technical difference behind a ceasefire versus a pause.” But other senior Labour figures said his remarks had done little to hold the parliamentary party together. One insider said Labour MPs were stressed, desperately trying to stop their colleagues at the national and local level from resigning. This open letter to Starmer comes after at least 250 Labour Muslim councillors called on the leadership to call for a ceasefire. Starmer gave his most direct criticism yet of the Israeli bombardment, expressing “concern” over some of its actions and urging Israel to allow fuel to cross into Gaza. Speaking to an audience at the Chatham House foreign affairs thinktank in London, Starmer said: “While I understand calls for a ceasefire at this stage, I do not believe that it is the correct position now.” Starmer insisted he took collective responsibility – the principle that members of his frontbench team adopt a unified position – seriously, but he gave no indication he was about to sack those who had spoken out. “It is for me to address collective responsibility, I recognise that,” he said. He said a ceasefire would “freeze the conflict”, allowing Hamas to launch attacks against Israel again in the future. “Hamas would be emboldened and start preparing for future violence immediately,” he said, adding that he wanted instead to see a temporary “humanitarian pause” in fighting. The comments were a direct rejection of calls for a ceasefire made by, among others, the Scottish Labour leader, Anas Sarwar, the mayor of London, Sadiq Khan, and the mayor of Greater Manchester, Andy Burnham. At least 13 shadow ministers – including Alex Cunningham, Afzal Khan, Rushanara Ali, Andy Slaughter, Jess Phillips and Florence Eshalomi – have also joined calls for an end to the fighting. Starmer also refused to support the judgment of the UN among others that war crimes may have been committed during the bombardment of Gaza. “Israel has to act in accordance with the law,” he said. But he added: “I think it’s unwise for politicians to stand on stages like this or to sit in television studios and pronounce day by day which acts may or may not be lawful under international law.” His comments were criticised by Sacha Deshmukh, the chief executive of Amnesty International UK, who said: “In failing to call for an immediate ceasefire, Keir Starmer is not showing the clear and principled leadership that this decades-old crisis needs.” He said it was “deeply disappointing” that Starmer “did not use this moment to be clear that under his leadership the UK would be consistent and rigorous in supporting international law”.