Labour is talking up the prospect of a May 2024 general election, with the shadow cabinet minister Emily Thornberry saying it was “the worst kept secret in Westminster” that a contest would be called then. Thornberry told Sky News on Thursday that the government’s decision to announce a budget in early March – the earliest date in 13 years apart from during the pandemic – “seems to confirm” that May is the most likely date. The party has been preparing for a May contest, despite most of Westminster expecting Rishi Sunak to wait until the autumn or winter. Leaving it to the latest possible time would give the Conservatives more hope of recovering in the polls, where they trail Labour by 15-20 points. The decision to call a budget on 6 March with hefty tax cuts still leaves open the option of a May election should the prime minister’s fortunes improve. If he fails to call an election in May, Labour may start to spread the narrative that Sunak is a “bottler” and “squatting” in Downing Street, which were the tactics used by the Conservatives against Gordon Brown in 2009 and 2010. Thornberry said Labour would be ready for an election. The Guardian reported this week that the Labour leader, Keir Starmer, has told shadow ministers to have their policy proposals ready by mid-January, in time for the manifesto to be completed by 8 February. He will also embark on a series of public question-and-answer sessions between January and March to highlight each of Labour’s five missions, which he hopes will define the election. “The whole country’s response is: bring it on,” said Thornberry, the shadow attorney general. “The country is desperate for a general election.” After the chancellor, Jeremy Hunt, announced the March date for the budget, Labour said it believed it pointed to a May election. A Labour source said: “Whatever they tell people, every decision the Tories have made has been geared to calling an election in May, if they believe that is to their advantage. “Labour will be ready whenever they call it, but for the country’s sake, the sooner people are given a chance to turn the page on the Tory years and make a new start, the better.” Hunt’s budget announcement swiftly prompted calls from backbench Tories for swingeing tax cuts, including the plan to slash inheritance tax that was missing from the autumn statement. The Telegraph has reported that Sunak’s government is thinking of scrapping it altogether as part of a wider “gear change” on tax in the budget. The Tory MP Jacob Rees-Mogg is among those calling for it to go, while fellow backbenchers Neil O’Brien and Jonathan Gullis want income taxes to be cut instead. A No 10 source said on Wednesday that the scrapping of inheritance tax was speculation, and not an idea being pushed by Downing Street. Asked about the possibility, Sunak’s deputy spokesperson declined to comment directly, but stressed both the limited scope of the tax – fewer than 4% of estates currently pay it – and the amount of money it raises. “On inheritance tax more broadly, the vast majority of estates do not pay inheritance tax, and the tax is forecast to contribute almost £10bn a year by 2028-29 to help fund public services that millions of us rely on,” she said.