In a speech in Hove, the Prime Minister confirmed 18 to 21-year-olds who have been out of work, education or training for six months would have to take on unpaid community work if they want to claim benefits.
He said that it was part of a mission by the Tories “effectively to abolish long-term unemployment” if they are returned to power after the general election on May 7.
“That well-worn path - from the school gate, down to the Job Centre, and onto a life on benefits - has got to be rubbed away,” he said.
The scheme will involve around 30 hours a week of community work from day one of their claim, which can involve making meals for older people or working for local charities alongside 10 hours of job hunting.
Mr Cameron said that it was essential to inject “order and discipline” to the lives of the of the so called “Neets” (young people not in employment, education, or training) before they were drawn irrevocably into a life on benefits.
“They drift from school to worklessness to benefits and not enough is asked of them. Now of course, the best thing is for young people not to fall into inactivity in the first place,” he said.
“But if they have drifted into a life of inactivity, then it’s pretty clear what these young people need. They need work experience. They need the order and discipline of turning up for work each day.
“So a Conservative government would require them to do daily community work from the very start of their claim, as well as searching for work. From day one they must play their part and make an effort.
“That could mean making meals for older people, cleaning up litter and graffiti, or working for local charities.
“Your first experience of the benefits system should be that yes, you can get help - but it isn’t something for nothing, and you need to put something back into your community too.”
The new proposals go a step further than already-announced Conservative plans to abolish Jobseeker’s Allowance for 18 to 21-year-olds and replacing it with a Youth Allowance.
After six months on the Youth Allowance, claimants will be required to undertake an apprenticeship or community work for their benefits. The allowance measure will apply to those who have been in work, education or training in the six months before their claim.
It is understood that the new plans will not apply to young people who have completed independent work experience in the six months before their benefits claim or the small number of university graduates who could be drawn into the scheme.
The Community Work Programme policy would apply to the roughly 50,000 new 18 to 21-year-old claimants a year who have been Neet for six months - around 10% of claims.
According to Downing Street, there is evidence that community work placements are more effective in moving claimants off benefits than the normal Jobcentre Plus signing on regime, and one pilot in London with specific requirements to work from day one proved even more successful.
The £20 million policy would be paid for from initial savings generated by the nationwide roll-out of Universal Credit.
The plans were attacked by the Liberal Democrats who said that young people needed to be helped into the workplace and not written off.
“These placements are not designed to help someone into work, more to punish. Just like the Tory plans to axe housing benefit for young people, it’s all stick and no carrot,” a spokesman said.
“Young people should be given help and support into the work place, help at job centres, and the opportunity to get on in life, not just written off as feckless and lazy.”
TUC general secretary Frances O’Grady said making young people carry out unpaid community work would mean they do not have time to find paid employment.
She said: “The Prime Minister who gave us a zero-hours jobs boom is now promising zero-pay jobs for young people.
“That isn’t an economy that works for young people, it’s an economy designed to work against them.
“Making young people work full-time for free means they will not be able to look for paid employment.
“Unemployed young people should be given a guaranteed paid job or proper training place, not forced into unpaid workfare.”