In a stump speech on Monday, Mr Sunak 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.
“If they get the kind of majority, the supermajority that the polls suggest, they will set about entrenching themselves in power. They will rewrite the rules to make it easier for them to stay in office and harder for anyone to replace them. So, don’t surrender your voice to Labour on Thursday. ”
The Prime Minister also sounded the alarm over national security, claiming that Russian president Vladimir Putin “does not want us to be re-elected”.
“Putin would like nothing more than for Britain to step back, to appease his aggression rather than face it down and that is what will happen with another party in power,” he told the Telegraph.
Sir Keir has previously criticised “desperate” Tory suggestions that Labour is a threat to national security, saying that his party has united with government on defence matters such as support for Ukraine.
Meanwhile, Labour urged voters to move to avoid “waking up on July 5 to five more years of economic chaos” as it accused the Tories of having presided over a “one rule for them and another for everyone else” approach to government.
“At the heart of the Tory campaign is the view that this is as good as it gets for the UK,” the party said.
“Yet living standards have stagnated since the Tories took office, NHS satisfaction levels are at their lowest levels ever recorded, and the first response of some of those close to the election decision was not to get ready to face the voters, but to call the bookies.”
It comes after the Prime Minister on Sunday insisted that the UK is a better place to live than it was in 2010 as he battles to narrow the gap in the polls.
Mr Sunak defended the Conservative record in government against what he described as a “declinist narrative” while he faced questions about the state of public services and the economy.
It was put to him that the UK has become poorer by many measures over the past 14 years the Conservatives have been in power, and that public services are deteriorating.
“I just don’t accept that,” Mr Sunak told the BBC’s Sunday with Laura Kuenssberg.
“Our schoolchildren are now the best readers in the western world.”
Labour said the remarks showed he was “out of touch”.
Shadow chancellor of the Duchy of Lancaster Pat McFadden said: “If people don’t want to wake up on July 5 to five more years of economic chaos, to wake up knowing that all the future offers is the same as the recent Tory past, then they have to vote Labour and vote for change on Thursday.”
Speaking to the Guardian newspaper, Sir Keir said the “hope has been kicked out of people” and vowed to bring an end to “divisive and toxic” culture wars if he makes it to Number 10.
In words published as exit polls showed Marine Le Pen’s National Rally party making gains in the first round of France’s parliamentary election, he suggested Labour would have to stave off a rise of the populist right.
Sir Keir said his party could do this by restoring faith in British politics through “deeds, not words,” citing his focus on economic growth.
Both Sir Keir and Mr Sunak will hit the trail on Monday for the final push in a six-week campaign, with the Labour leader touring the shires in southern England and the Prime Minister in the Midlands.
Meanwhile, Reform UK leader Nigel Farage is battling an ongoing fallout over allegations of racism within his party.
The latest flare-up came on Sunday when the Reform candidate for Erewash, Liam Booth-Isherwood, dropped out of the race to back Tory contender Maggie Throup after becoming “disillusioned” with what he described as a “significant moral issue” within party ranks.
It comes after Mr Farage faced accusations from across the political divide of failing to tackle allegations of racism within Reform which have engulfed the party in recent days.
Addressing a rally in Birmingham earlier on Sunday, the party leader insisted that “the bad apples are gone” after withdrawing support for three candidates over the row.
Campaigners for Reform in the Clacton seat Mr Farage hopes to win in Essex were also recorded by an undercover journalist from Channel 4 making racist comments, including about the Prime Minister, who is of Indian descent.
Party chairman Richard Tice claimed the candidate’s switch in support showed that Conservatives were offering inducements to Reform rivals “to persuade them to talk badly of Reform, stand down and then endorse the Tory candidate”.
“This shows dark forces at play by desperate Tories,” he wrote in a post on X, formerly Twitter.
Elsewhere on Monday, Liberal Democrat leader Sir Ed Davey will promote his party’s pledge to spend £440 million a year on supporting widows and bereaved children on a campaign visit in southern England.
Scottish First Minister and SNP leader John Swinney will be out in the north east of the country, claiming that only his party offers the “hope of a better future in the European Union” for Scotland.