Britain is facing some of the most dangerous few years in its history, Rishi Sunak will say on Monday in a speech intended to frame the general election as a generational tussle for the long-term future of the country. The prime minister will give a speech in central London in which he will lay out what he believes to be at stake at the next election, as he warns the UK faces threats from international conflict, migration and technology. The speech, which aides say Sunak has wanted to give for a while, is an attempt to shift political focus away from the turmoil that has engulfed the Conservative party for the last few years and helped give Labour a 20-point poll lead. He is expected to say: “I have bold ideas that can change our society for the better, and restore people’s confidence and pride in our country. I feel a profound sense of urgency. Because more will change in the next five years than in the last 30. “I’m convinced that the next few years will be some of the most dangerous yet most transformational our country has ever known.” Sunak has endured a difficult two weeks as prime minister, seeing his party crash to heavy defeats in local and mayoral elections and then watching Natalie Elphicke, one of his backbench MPs, defect to Labour. Tory strategists, however, believe he has emerged stronger from this period. A long-threatened attempt by Conservative MPs to unseat the prime minister after this month’s local elections failed to materialise, meaning he is all but guaranteed to be party leader until the national polls. Senior Tories also believe Elphicke’s defection may end up backfiring on Labour given the controversy over her attempts to influence the judge overseeing the 2020 trial of her then husband, Charlie Elphicke, on sexual assault charges. Sunak’s aides believe he may be able to pull off an unlikely win at the general election partly by presiding over a continued economic recovery and partly by turning it into a personal contest between himself and the Labour leader, Keir Starmer. Sunak is overwhelmingly unpopular with the electorate, with a net approval rating of -59 according to Ipsos Mori, as bad as any prime minister on record. Starmer is also unpopular, however, with a net approval rating of -31, and the Conservatives are hoping to capitalise on voters’ doubts about him. Sunak will focus in his speech on three threats facing the world in general: war, migration and the rapid advance of technologies such as artificial intelligence. He will argue that he and his party have a plan for each, in contrast with Labour. He will highlight his party’s promise to spend 2.5% of economic output on defence by the end of the decade, a timetable Labour has refused to back, saying it would instead meet the target “as soon as resources allow”. Sunak will talk about his policy of sending asylum seekers to Rwanda, a plan Labour has promised to scrap and use the money instead on tackling people-smuggling gangs. He will also mention the way he has led international attempts to regulate AI, including hosting last year’s inaugural international summit at Bletchley Park. The prime minister will say: “Our country stands at a crossroads. “Over the next few years, from our democracy to our economy to our society – to the hardest questions of war and peace – almost every aspect of our lives is going to change. “How we act in the face of these changes – not only to keep people safe and secure but to realise the opportunities too – will determine whether or not Britain will succeed in the years to come.” Those close to Sunak say he will not set out when he intends to hold an election, instead sticking to the line it will come in the second half of this year. The foreign secretary, David Cameron, urged the prime minister on Sunday to hold out until late this year. “The longer actually we have between now and the election, the more you’re going to see the plan is working,” he said.