Labour risks losing in a number of its target seats as previously loyal progressive voters turn away from the party, senior party figures and polling experts have warned. Experts said Keir Starmer’s party could struggle to win as many as a dozen of its key targets, and could even lose two of the seats it now holds, as a result of alienating some Muslims and younger progressive voters angered by its stance on Gaza and the climate crisis. Polls have suggested the party is on track to win a landslide victory at this year’s general election. But if the margins narrow significantly, some Labour insiders fear the desertion of parts of the party’s core vote could prove to be the difference between a hung parliament and an outright majority. One senior Labour adviser told the Guardian: “Are we losing urban progressive voters? Of course. At the moment it looks like it doesn’t matter as our poll lead is so wide, but it could hurt if they narrow and those voters don’t come back. “What it really means is that a lot of Labour MPs who assumed their seats were super safe will have to spend more time this year campaigning in their own seats than they might have expected.” Patrick English, the director of political analytics at YouGov, said: “If there is a big anti-Labour feeling among Muslim and young voters, that could cost them in a big way in places where those groups make up 10-15% of the population each. “If the polls are level or even if Labour is five points ahead, it could be extremely damaging for Labour and could mean they fail to win a whole host of English bellwether marginal seats.” Polls have shown Labour about 20 points ahead and heading for a majority of more than 150 seats. Last month it emerged that the party lost 23,000 members – from 390,000 in January to 366,600, according to figures released to its national executive committee. The decision by Starmer, the Labour leader, to tack to the right on issues such as the economy, immigration and the environment has helped win over older white voters who backed Brexit at the referendum. But those decisions have also upset many traditional Labour voters in urban areas in particular. Among those voters’ chief concerns is the party’s decision to abandon its commitment to spend £28bn a year on green projects and Starmer’s defence of Israel’s military actions in Gaza. A poll released last week by YouGov showed the party has lost ground in more than 50 seats since 2019, an unexpected finding given that Labour has gained 12 percentage points in the polls since then. Labour officials said that under the previous leader, Jeremy Corbyn, the party stacked up votes in otherwise safe seats, and that by moving to the right, it is now spreading its vote more evenly across the country. However, it has unexpectedly put two Labour seats – Bristol Central and Sheffield Hallam – at risk, and could make the difference in as many as a dozen more target seats that are expected to be close. One Labour campaigner in an urban seat said: “Climate has been the big issue for us on the doorstep. Voters here are very politically engaged and are very aware of what has happened to our green plans. That is the number one reason why people are thinking of voting green instead.” Other seats where Labour has dropped significant support include Birmingham Ladywood and Liverpool Riverside. Both are safe Labour seats and unlikely to fall at the election, but the drop has alarmed some local campaigners who say they are having to make more of an effort campaigning to make sure they remain secure. The bigger risk, say experts, lies in northern “red wall” seats that Labour must win to gain a majority but where the majorities it is trying to overturn are so large that any splintering of the progressive vote could cost it victory. Shaffaq Mohammed, the Liberal Democrat candidate in Sheffield Hallam, which was once held by Nick Clegg but has been Labour since 2017, said: “Sheffield has traditionally been a left-of-centre city. Keir Starmer embracing some of the Conservative policies such as the two-child limit on benefits has not gone down well here.” Mohammed added that voters in the constituency, many of whom are students, often brought up Labour’s response to Gaza, and especially an LBC interview in which Starmer seemed to say Israel had the right to withhold water and power from the Gaza Strip. The Labour leader has since said that was not his position, but many of the party’s MPs said the interview had resonated with their voters. Some said the real risk to Labour was not at this election, where the Conservatives show little sign of reversing the collapse in support they have suffered in the last two years, but at the following election, where they would not be able to run as anti-incumbents. Sunder Katwala, the director of the non-partisan thinktank British Future, said: “This is a 2025 or 2028 challenge for Labour. There is a danger of taking your core vote for granted, and that danger will be very apparent after the election.” A Labour spokesperson said: “We’ve had a deliberate strategy to broaden our electoral appeal by changing the Labour party and putting it back in the service of working people. We don’t take any support for granted and we will continue to work to win back any support we’ve lost ahead of the general election.”