Labour would use a landslide victory to shift politics to the left and stay in power for decades, Rishi Sunak will warn on Monday, as he launches a last-ditch attempt to persuade Conservative voters to turn out for Thursday’s election. The prime minister will address a rally at the beginning of the final week of the election campaign, which polls suggest will end in the Conservatives being ousted from power. Sunak will repeat his recent warnings about the dangers of a Labour “supermajority”, even as his Conservative colleagues begin to jostle for position ahead of an expected leadership contest after the election. The prime minister will say: “We have four days to save Britain from a Labour government. Labour would hike taxes by more than £2,000 for every working family, would shunt our politics to the left and change the rules to ensure that they can stay in power for decades.” He will add: “I tell you this: once you have handed Keir Starmer and Labour a blank cheque, you won’t be able to get it back.” The Conservatives have shifted tactics several times within the campaign, going from making a flurry of policy announcements, to accusing Starmer of planning secret tax rises, to talking up the chances of a historic Labour win. The party has repeated a highly contested claim about Labour raising taxes by £2,000 throughout the campaign. Labour continues to enjoy a 20-point poll lead heading into the final few days before polling day, with MRP models suggesting the party could win a majority of more than 250. Party sources, however, say they believe the most recent warnings about a landslide victory for their party may be resonating with Conservative voters who otherwise were planning to stay away on polling day. Sunak insisted on Sunday he was proud of the campaign his party had run. “This campaign has shone a spotlight on the fact that a Labour government is going to raise everyone’s taxes and they’re not being straight with everyone about it, and I’m proud of that,” he told the BBC. But while the prime minister focuses on the final few days of campaigning, there are already signs his party is preparing for a leadership election to come. Kemi Badenoch, the business secretary, declined to rule out a leadership bid in an interview with the Times over the weekend. “We would need to be looking at what the party’s offer is going to be, how we rebuild,” she said. “I just think that’s a question for much later.” Meanwhile, senior Tories have told the Mirror they want to make sure Oliver Dowden, the deputy prime minister, does not take over the leadership on a caretaker basis should the party lose next week. Dowden told Sky News over the weekend that rumours about his candidacy were “total and utter nonsense”. The Times revealed on Sunday that leadership websites for several senior Tories, including Badenoch, the former home secretary Stella Braverman, and the leader of the Commons, Penny Mordaunt, had been either set up or updated in recent weeks. With his party focusing on what might come after the election, Sunak sought on Sunday to defend his party’s record after 14 years in power. He told Laura Kuenssberg: “[This] is a better place to live than it was in 2010. Of course, I understand that the last few years have been difficult for everyone – we had a once in a century pandemic, followed by a war in Ukraine that drove up everyone’s bills – and of course, that’s been difficult for everybody.” Economic data suggests, however, that the country is worse off than in 2010 on a number of counts. Figures from the Institute for Fiscal Studies show growth has never recovered to its pre-2008 trend, leaving each person on average £10,900 worse off as a result. Real wages have shown almost no growth since 2010, while business investment is well below its pre-Brexit level. Kuenssberg confronted the prime minister with a series of messages from BBC viewers that suggested voters were not persuaded by Sunak’s upbeat message. One person asked: “Why isn’t anything working in this country?” and another, called Sheila, said: “Our biggest worry is not about tax. It’s about having the basics.”