Keir Starmer is on course to clinch a landslide majority of 140 for Labour at the next UK general election, the first modelling based on a megapoll of new constituency boundaries suggests. With the Conservatives still suffering from a large polling deficit, Labour’s support was found to be at about 35% – 12% ahead of Rishi Sunak’s party. However, Labour’s support was said to remain “quite soft”, with a “worst case scenario” model showing it could end up the biggest party in a hung parliament. The results were revealed in an analysis of polling known as multilevel regression and post-stratification (MRP), and will boost Starmer’s hopes of victory as the long campaign in the run-up to the next election progresses. Prof Sir John Curtice said since the sleaze scandals that engulfed Boris Johnson and Liz Truss’s mini-budget, there had been a “very substantial” drop in support for the Tories. Though Sunak had sought to steady the party, Curtice said there had been only “a bit of a narrowing” of Labour’s lead. The general election poses a headache to pollsters and campaign strategists, as constituency boundaries are being redrawn for the first time in several election cycles. In the first MRP based on the new boundaries – conducted by FocalData and commissioned by the Best For Britain campaign group – Labour’s potential success was said to be under varying degrees of risk. If the Reform party – the reincarnation of the Brexit party – repeats the tactic used in 2019 of standing aside in Tory marginals, Labour’s seats would still be at a healthy 401, leaving the Conservatives on 202. Another scenario has Labour winning 370 seats to the Tories’ 232, based on redistributing undecided voters by their education profile. If both were combined, under what was billed as Labour’s “worst-case scenario”, the model predicts a hung parliament – with the party about a dozen seats short of a majority, with 316, leaving the Tories at 286. The poll of 10,140 voters was undertaken between 20 April and 9 May. Labour is projected to be on course for a major comeback in Scotland. Best for Britain said the poll showed the SNP was “bleeding voters” to “don’t knows”, meaning Labour was likely to pick up as many as 31 seats. Sunak was more popular than the Conservatives and therefore “might be able to turn his party around”, said Curtice. But he added that the Tories “are a long way behind”. Stories about Sunak previously possessing a US green card and his wife’s non-dom status “did a damage to him from which he has, frankly, personally never recovered”, said Curtice. Luke Tryl, the UK director of the More in Common group, said there was “the potential for quite a large” Labour victory – but cautioned the party should not be complacent because it could merely be “winning by default”. He added Labour’s support remained “quite soft” and that the party that would win the next election was the one that could “best convince people that it’s OK to turn on the six o’clock news and not be worried”. In focus groups, Tryl said voters found Sunak to be competent and credited him for the furlough scheme, adding that he was outperforming his party. “An emerging theme from the focus groups is ‘is he strong enough?’ And that’s exacerbated by the constant returns to the stage of Boris Johnson.” In the event of a Tory leadership contest, Tryl said Kemi Badenoch and Penny Mordaunt were potential frontrunners, but said of the home secretary, Suella Braverman: “I do know from testing in both focus groups and polling that Suella would be a ‘longest suicide note in history’ type candidate for the Conservative party, simply because she is so polarising.”