Sadiq Khan has become the most senior Labour politician to call for an immediate end of UK arms sales to Israel, with a number of other prominent party figures also saying the government should take action after the killing of seven aid workers in Gaza. The London mayor said Rishi Sunak must halt arms sales, saying: “It’s got to stop.” Margaret Beckett, who served as foreign secretary under Tony Blair, said ministers should very seriously think about halting the sales of weapons if there was a risk of them being used in the sort of attack on the food convoy on Monday, in which three Britons were among those killed. Charlie Falconer, the Labour peer and Blair-era justice secretary, said it was “absolutely critical” that the government set out its legal position publicly, so it could show a justification for not halting arms sales. The interventions came as a tally of public statements by the leftwing Labour group Momentum showed that more than 50 Labour MPs had also demanded an end to arms sales, a quarter of the party’s total in the Commons. The position is distinct from the official Labour stance: David Lammy, the shadow foreign secretary, has said UK arms sales should be halted only if government lawyers conclude there is a risk the weapons could be used to commit serious breaches of international law. Speaking to the Politics Joe website, Khan said he was dismayed at the way Israeli forces appeared to have “targeted” a marked aid convoy run by the food charity World Central Kitchen. “In my view, the fact the government is not publishing the legal advice, one can only draw one conclusion,” Khan said. “I think the government should be pausing all sales of weapons to Israel. I think we should be holding to account the Israeli government.” Beckett, who will step down at the next election, 50 years after first being elected as an MP, told the Guardian: “I’m normally cautious about the easy assumption on suspending arms sales. “But if it appears that arms sold by Britain could be used in the kind of attack that took place on Monday in which Brits who were there to help humanitarian efforts were killed, then support should suffer. The government should give this serious consideration.” Falconer said: “When the government participated in the Iraq invasion and the Libyan incursion, without giving all the detail of the legal advice, they published what the reasons were. The government now needs to do at least that – it needs to explain what its position is. “We’re seeing a terrible suffering in Gaza … The evidence is mounting of the unbearable damage being done to non-combatants. So why is it not a breach? They’ve got to offer some explanation. What is the basis on which the British government is concluding that they do not have to revoke these [arms] licences?” A senior Labour figure said that while the military significance of ending arms would be minimal, “the symbolism will be immense”. They said they believed Labour was moving “in the direction” of calling on the government to do that, but that there was a need for Keir Starmer to be cautious: “If there’s any complacency, by the end of the year he’ll be prime minister and he’ll be in a bad position to deal with the White House. “He’s known from day one that he’s not completely at liberty to assert his own resilience.”