Labour can win under Keir Starmer’s leadership if the party makes major changes to curb the influence of internal factions, Peter Mandelson has said in an article for the Guardian. Lord Mandelson, who was Tony Blair’s first secretary of state and MP for Hartlepool, is said to have offered informal advice to Starmer’s team, though he has no defined role. His interventions after the loss of the Hartlepool byelection that Labour should cut links with leftwing factions, including trade union figures, caused an outcry among union leaders and MPs on the left of the party. Mandelson wrote that his comments had “touched a nerve” and that he was not attacking trade unionism and its links to Labour, but “the power of hard left factions that abuse it”. He named Unite’s Len McCluskey and Aslef’s Mick Whelan, the latter of whom wrote to Starmer on Monday demanding the Labour leader publicly repudiate Mandelson’s comments. Mandelson said the party needed to make urgent changes so it could face outwards, rather than struggle with internal battles. “A different party culture and rulebook needs to protect [Labour politicians] from party factionalism so that they can face the country and not just the membership,” he said. “The members themselves need protection from harassment and bullying, and the candidates they select to fight future key seats need better to reflect our communities rather than the choices of union barons. “Party activists need to be out talking to voters, not stuck in endless meetings arguing over minutes and matters arising. This programme of party reform is urgent, alongside policy changes that ensure we have a manifesto that wins voters over and does not just make the faithful feel virtuous.” Tensions within the shadow cabinet blew up over the weekend over Starmer’s reshuffle. Mandelson warned of the risk of sabotaging Labour’s election prospects. “We hold victory at the next election in our own hands. We can either talk about change while wanting everything to remain the same or we can face up to the task of transformation on which our success depends,” he said. “This requires the whole of the party closing ranks behind change and giving Starmer his chance to lead so that the party we love does not lose, lose, lose, lose and lose again following our 2010 defeat.” He said Labour’s policy review, which will be undertaken by the demoted former shadow chancellor, Anneliese Dodds, should be future-facing, including looking at how the success of the vaccine programme could be applied to other industries. “Boris Johnson’s luck will not last for ever. Politics isn’t like that. The vaccine delivery is the principal thing propping up the government’s popularity,” he said, saying many traps lay ahead for the Tories including over their failure to deliver on social care, raising taxes while holding down spending rises on public services, and the independence debate in Scotland. John McDonnell, who was the shadow chancellor under Jeremy Corbyn, said on Monday that Mandelson’s vision would only cause further division. “The reshuffle fiasco caused unnecessary divisions in the party at the weekend. Now our affiliated unions are being alienated by exposure of Mandelson’s strategy for Labour’s future. Unless Keir Starmer curtails Mandelson’s influence there will be more division.”