Keir Starmer has been told that Labour risks taking its Muslim voters for granted, as MPs said the party had a fight on its hands to win back support lost over its position on the Israel-Gaza war. The warning came after George Galloway swept to a stunning victory in the Rochdale byelection, winning nearly 40% of the vote after a contest beset by chaos and controversy, dominated by the Middle East conflict. The party’s biggest internal Muslim group said the result showed Starmer faced a “full-blown crisis”, while Neal Lawson, the director of the cross-party campaign organisation Compass, said Labour could be facing a slow collapse in support like that seen in the “red wall” and Scotland. After a campaign viewed as one of the more ill-fated and divisive in recent political history, Azhar Ali, cut adrift by Labour after inflammatory comments about Israel, limped home in a distant fourth place, winning just 7.7% of the vote. The decision to drop Ali came too late for Labour to nominate a replacement. “Galloway only won because Labour didn’t stand a candidate,” Starmer said on Friday. “I regret that we had to withdraw our candidate, and apologise to voters in Rochdale.” While it is possible that someone with the backing of Labour’s electoral machine could have held a seat that was won by nearly 10,000 votes in 2019 by the late Tony Lloyd, such a storming win for Galloway has spooked some in the party. “We’ve got a real fight on our hands,” one senior backbencher told the Guardian. “It will be messy. The Workers party [Galloway’s party] will stand candidates in large parts of the West Midlands, Birmingham, Pennine towns and areas like Redbridge, Waltham Forest and Newham where the Labour vote has split over Gaza. “Galloway’s win will also embolden other independent groups supporting prospective candidates. It’s going to be vicious and feel as though Labour has lost its grip, which simply isn’t true. We just need to strengthen our messaging.” The chair of the Labour Muslim Network said the party was “at crisis point” on the issue. “There is no doubt that there are some extenuating and extraordinary factors in Rochdale which won’t be repeated around the country,” said Ali Milani, a former Labour parliamentary candidate who has been critical of the party over Gaza. “But I think anyone who suggests that this isn’t evidence of a serious problem Labour has with the trust and support of the Muslim community, who Labour has enjoyed the support of for decades, is just burying their heads in the sand.” Lawson said that while it remained to be seen whether Rochdale was “a blip or part of a more seismic trend in terms of the Muslim community’s support for Labour”, the party should be mindful of how the first-past-the-post voting system (FPTP) had previously disguised slow collapses in Labour support in Scotland and northern “red wall” seats. “FPTP encourages Labour to take its big blocks of voters for granted in the presumption that they have nowhere else to go,” Lawson said. “The SNP, then Ukip/Brexit and via them the Tories, and now Galloway have proven to be alternatives. Labour MPs and candidates in seats with big Muslim votes will be nervous today. People don’t like being taken for granted.” Another MP said the problem with Gaza went wider than Muslim voters, given evidence of significant overall public support for a ceasefire. Nevertheless, senior Labour figures argued that too much should not be read into what one called a “unique” byelection. “We have lost support over this conflict in the short term. But it shouldn’t be overstated,” they said. “Galloway is a terrible man. We’ve seen this movie before. He gets into parliament and doesn’t really do anything before losing at the election.” A series of independent prospective candidates basing their campaigns on pro-Palestine messaging, including some ex-Labour councillors, plan to stand in May’s local elections in places including Bradford. “It can be easier for independents running for councils and if a whole lot of them won that could be worrying,” a Labour local government source said. “But at the same time, people pay less attention to local elections.” Rob Ford, a professor of politics at Manchester University, said any notable success for candidates standing on a pro-Palestinian footing in May would be “a big headache” for Starmer and his team. “Even the perception from some Labour MPs that they face a risk, whether or not that is real, means they will want help in the general election,” Ford said. “If you’re trying to win 150 target seats to get a majority, you really don’t want to be diverting resources to seats you thought were already in the bag.” Galloway, the hugely controversial former Labour MP who has previously won seats from his former party in Bethnal Green and Bow and in Bradford West, used a victory speech interrupted by hecklers to herald what he called “a shifting of the tectonic plates” in British politics. The wider result, however, pointed more towards the chaotic picture, with David Tully, a local businessman who stood as an independent, coming second ahead of the Conservative Paul Ellison, who spent a good chunk of the campaign away on holiday. The Reform candidate, Simon Danczuk, a former Labour MP who was suspended from the party in 2015 after sending inappropriate messages to a teenager, was sixth. Ford said: “If you were ask a political scientist to design a byelection in which it would be impossible to draw any wider lessons, it might look a bit like this one.” The Board of Deputies of British Jews said Galloway’s win was “a dark day for the Jewish community”, describing him as “a demagogue and conspiracy theorist, who has brought the politics of division and hate to every place he has ever stood for parliament”.