Labour is at odds with Full Fact, the independent factchecking charity, after it claimed the party’s energy price cap freeze was underfunded by at least £5bn. The party said Full Fact had got its sums wrong, saying the charity did not understand how direct debit works. However, Full Fact was standing by its analysis on Friday, which said the party had not taken into account that people use more energy in the winter, causing Labour to underestimate the cost of freezing bills by at least £5bn, or £340 a household. In response, it is understood that Labour is sticking by its sums, because direct debits are not meant to be above the level of the price cap regardless of higher usage in winter. Keir Starmer announced his plan for a freeze on the current price cap at £1,971 earlier this summer, funded partly by a higher windfall tax on the profit of oil and gas companies. Ofgem, the energy regulator, announced that the price cap would increase to £3,549 from October. The rise puts pressure on the next Conservative prime minister, likely to be Liz Truss, to announce measures to cut bills for households and businesses. Starmer has said his plan would save the average household £1,000 and said he did not rule out increasing funding if necessary, while insisting that the proposal was currently fully funded. “What we’ve got is a fully costed, comprehensive plan for this winter which will freeze those prices – that is welcome news to so many people who are worried sick today,” he told broadcasters. “I accept that in April, May next year we need to look forward then to the proposals in place. “That’s why I’ve said, alongside our plan, we need medium and long-term solutions. We need to be much more self-sufficient when it comes to energy.” Findings from economists at the Institute for Fiscal Studies (IFS) thinktank suggest the total cost of the plans could be even higher, at roughly £8bn more than Labour’s projected price tag of £29bn. Will Moy, the chief executive of Full Fact, called for politicians to “own up to their mistakes” if they wish to be trusted by the electorate. “Labour’s plan set out to tackle a serious problem, but the party’s ‘fully funded’ proposals do not add up in a way that would cover bills this winter,” he said. “When politicians fall short, we can demand better. Politicians must own up to their mistakes if they’re serious about earning voters’ trust.”