Rishi Sunak lied to the country and broke the ministerial code when he claimed Labour’s spending plans would increase taxes by £2,000, Keir Starmer has said, as his party attempts to regain control of the election narrative. Both Starmer and the shadow chancellor, Rachel Reeves, rounded on Sunak in an increasingly bitter and personal war of words, saying the prime minister’s tactics during Tuesday night’s TV debate showed he was dishonest under pressure. The Conservatives were jubilant at how the figure had landed on Tuesday night, and some Labour insiders were privately horrified at how slow Starmer had been to challenge the tax claims during the debate. But a new YouGov poll 24 hours later threatened to shatter their moment of hopefulness, putting Reform within two points of the Tories, and Labour on 40%. Both parties are expected to launch their manifestos next week. There was a flash of panic in Labour as Sunak repeatedly said during ITV’s head-to-head debate with Starmer that “independent Treasury officials” had costed Labour’s policies “and they amount to a £2,000 tax rise for everyone”, an assertion the Labour leader initially struggled to counter. The party launched a counteroffensive on Wednesday morning with videos accusing Sunak of lying, the first time the party has levelled that accusation. To make the case, Labour released a letter from James Bowler, the Treasury’s permanent secretary, in which he said ministers should not suggest civil servants had produced the figure. Starmer said he believed Sunak should be investigated for breaching the ministerial code. “What you saw last night was a prime minister with his back against the wall, trying desperately to defend an awful record in office, resorting to lies,” Starmer said in a round of media interviews during a D-day-related visit to Portsmouth’s dockyard. “He knew very well what he was doing. He lied about our plans. And that is a true test of character. As we go to the polls it is important for voters to know about the character of the two individuals who want to be prime minister.” He added: “The prime minister revealed his character last night: someone who resorts to lies when he’s under pressure.” Asked if he believed Sunak had breached the ministerial code and if he would back an investigation, Starmer said: “Yes, he breached the ministerial code because he lied.” The election, he said, was “a choice between chaos and division, and now lies on top of it”. In a letter to Darren Jones, the shadow Treasury chief secretary, sent on Monday, Bowler said the document “includes costs beyond those provided by the civil service”. He wrote: “Costings derived from other sources or produced by other organisations should not be presented as having been produced by the civil service. I have reminded ministers and advisers that this should be the case.” Starmer, who went for a trip around the harbour in a D-day-type landing craft with passengers including Len Chivers, a second world war veteran, dodged questions about whether he had known about Bowler’s letter before the debate, and if he had been too slow to rebut the figure, which Sunak used repeatedly. “What matters is the facts. All of our plans are fully costed or fully funded,” he said. Claire Coutinho, the energy secretary and one of Sunak’s closest allies, had earlier doubled down on the attack, saying the figure came from “official costings from the Treasury”. When asked whether the Treasury had calculated the figures based on “assumptions from special advisers”, Coutinho told BBC Breakfast: “I can tell you that these are brilliant, independent civil servants and they would not be putting anything dodgy in there.” She later said the claimed tax rise would be “over the course of parliament. It’s £2,000 over four years,” when speaking to BBC Radio 4’s Today programme. Conservative strategists also plan to stick with the attacks and have defended using the costings. Sunak tweeted the £2,094 figure again on Wednesday. The Conservatives also challenged Labour to rule out further potential taxation, as they launched a “family home tax guarantee”. The chancellor, Jeremy Hunt, said on Wednesday that the party would rule out changes to council tax bands and cutting discounts, would maintain protections on homes from capital gains tax, and would not increase stamp duty. Labour said it would match all those pledges and said the Tories had already raised billions of pounds in increased council tax. In his media interviews in Portsmouth, Starmer reiterated that there would be no further tax measures apart from the ones Labour had already set out, saying : “All of Labour’s plans are fully costed and fully funded. They do not involve tax rises for working people.” Asked about inheritance tax, Starmer said: “We have no plans to raise inheritance tax. In fact, none of our plans involve tax rises over and above the ones we’ve spelled out because all of our plans are fully costed and fully funded. But it is very important that I get across that we will not be increasing tax on working people, so no increase in income tax and national insurance or VAT.” Both Starmer and Sunak will be in Normandy on Thursday for the commemoration marking the 80th anniversary of D-day.