School-leavers could be forced to do community work under a Conservative government, David Cameron has said.
He said full details had yet to be worked out but options included a compulsory scheme lasting four months, with lottery cash as a funding option.
The Tory leader told the BBC he would be discussing the idea with voluntary groups, including The Prince's Trust.
He said the scheme would promote public service and tie in with the party's belief in "trust and responsibility".
He said trusting people and sharing responsibility would be at the heart of his Conservative Party, which he claimed was heading "into the mainstream of British politics".
In a speech last July, Mr Cameron spoke of his desire to create a "new National Movement" to replicate the sense of shared achievement experienced by people of his father's generation who did national service.
"We should view this new enterprise as something for every young person in our country. An essential part of growing up to be a British citizen, not just an add-on extra for a select few", said Mr Cameron in his speech.
But he did not suggest at this stage that such a scheme might be compulsory.
Liberal Democrat leader Charles Kennedy responded to the plan by saying the Liberal Democrat Youth Taskforce was already exporing a similar scheme.
"David Cameron wants to portray himself as a liberal but needs to be careful to attribute his 'ideas' to those who are genuinely doing the fresh thinking," he said.
The proposal comes as Mr Cameron launched a new group to develop policies on the key election battlegrounds of health and education, chaired by educationalist Baroness Perry and former Health Secretary Stephen Dorrell.
Policy chief Oliver Letwin promised more detailed policies than at the last election when the Conservatives simply pledged "cleaner hospitals and better discipline".
Speaking at the launch of the policy review at the party's London headquarters, Mr Letwin admitted the party "had to learn" from the electorate's rejection of this stripped-down approach.
But Baroness Perry stressed the policy review was not about revamping the structure or funding of health and education - but rather about how to set professionals free to do their jobs effectively and deliver quality services.
She said people have had enough of public services "constantly being pulled up by the roots" by central government.
And she attacked Labour's targets and inspection regime.
"I think over recent years we have demoralised our professionals by this emphasis on bad teachers, bad schools, bad doctors.
"Every walk of life has people in it who are less than perfect. In any organisation there are going to be some people who are not pulling their weight or are not up to it.
"But that is a management issue. It's not an issue for central government," she told reporters.
Other policy groups launched by Mr Cameron include one looking at global poverty advised by Bob Geldof, another on green issues chaired by environmentalist Zac Goldsmith and one on social justice, chaired by Iain Duncan Smith.
The reviews are due to deliver their recommendations in 18 months time, when they will form the basis of Conservative policy at the next election.