Under the plan, a small minority of 18-year-olds — 30,000 out of an estimated 700,000 — would spend 12 months in the military, working in areas such as logistics or cyber defence.
The rest would spend one weekend a month working for charities, community groups, or organisations such as hospitals, the police and the fire service.
Sunak said the program would help “create a shared sense of purpose among our young people and a renewed sense of pride in our country”.
It remains unclear how it will be made compulsory. Home Secretary James Cleverly said no one would be forced to serve in the military.
Cleverly said Sunday that the main goal of the new plan was not boosting the military but building “a society where people mix with people outside their own communities, mix with people from different backgrounds, different religions, different income levels.”
The Conservatives estimated the cost of the national service plan at £2.5 billion ($4.7 billion) a year. They said it would be paid for partly by taking £1.5 billion ($2.9 billion) from the UK Shared Prosperity Fund, which was set up in 2022 to regenerate poor communities.
Labour said the national service announcement was a “desperate £2.5 billion unfunded commitment” from a party “bankrupt of ideas”.
Former Labour Home Secretary Alan Johnson said the Tory plan amounted to “compulsory volunteering” and predicted “it’ll never happen”.
Elections in the UK have to be held no more than five years apart. The prime minister can choose the timing within that period and Sunak, 44, had until December to name the date.
The Conservatives, who have been in office for 14 years, are trailing the opposition Labour Party led by Keir Starmer in opinion polls and are trying to overcome a widespread sense that voters want change.
Sunak’s election announcement outside 10 Downing Street saw him drenched with rain and drowned out by protesters blasting a Labour campaign song.
One of his first campaign stops was at the Belfast shipyard where the doomed ocean liner Titanic was built — another detail seized on gleefully by opponents.
Voters will elect lawmakers to fill all 650 seats in the House of Commons.
The leader of the party that can command a Commons majority – either alone or in coalition – will become prime minister.