Rishi Sunak has said he will introduce a new form of mandatory National Service for young people if the Conservatives win the general election.

In the first new policy announcement of the campaign, the prime minister has unveiled a plan that would see 18-year-olds given the choice of a full-time military placement for 12 months or a scheme to volunteer for one weekend a month for a year.

The placement would be selective – with tests used to decide who is eligible – and involve working with the armed forces or in cyber defence.

The voluntary option would see young people spending 25 days with organisations such as the police, the fire service, the NHS, or charities that work with older isolated people.

General election latest: Details of Sunak’s helicopter travel revealed

Mr Sunak said the new model would provide “life-changing opportunities for young people” and allow them to learn “real world skills”.

Writing in the Mail on Sunday, the PM said: “To those who complain that making it mandatory is unreasonable, I say: citizenship brings with it obligations as well as rights. Being British is about more than just the queue you join at passport control.”

The Tory party has also suggested National Service would cut crime, saying research shows volunteering can increase social responsibility.

The specifics of the plan would be established through a new Royal Commission – a type of advisory committee set up to investigate significant issues.

Conservative sources said that the commission would look at possible non-criminal sanctions for any teenagers who refused to take part in National Service.

Details such as exemptions from the scheme would also be established through this body.

National Service came into force in January 1949, and meant all physically fit males aged between 17 and 21 had to serve in one of the armed forces for an 18-month period, with the period lengthened in 1950 to two years.

It ended in 1960, though the last national servicemen were discharged in 1963.

The Conservatives estimate the programme would cost £2.5bn a year by 2029/30 funded with cash previously used for the UK Shared Prosperity Fund and by cracking down on tax avoidance and evasion.

Responding, a Labour Party spokesperson said the announcement was “desperate” adding: “This is not a plan – it’s a review which could cost billions and is only needed because the Tories hollowed out the Armed Forces to their smallest size since Napoleon.”