Charities and unions have hit out at David Cameron's plans to make some teenagers carry out community service from the moment they make a benefits claim.

Critics said that the move was akin to forced labour, did nothing to create opportunities for young people and risked cutting the number of full-time paid jobs in communities.

Mr Cameron defended the plan saying that it would "restore real fairness to our country" and the economy.

The Conservatives unveiled the measure as part of their plan to abolish long-term youth unemployment.

If the Tories win May's General Election 18 to 21-year-olds "at risk" of spending a lifetime on benefits will be forced to work 30-hours-a week to receive benefits and spend another 10 hours looking for work.

The clampdown is expected to affect 50,000 young people across the UK, including thousands in Scotland, who are not in education, employment or training for six months before they claim welfare.

Peter Kelly, director of the Poverty Alliance, said: "It is difficult to see how forcing a young person to carry out community service for 30 hours a week for a grand total of £57 will help prepare them for the real world or find employment.

"Young people want to work and policies such as this simply result in their stigmatisation."

Citizens Advice Scotland policy manager Keith Dryburgh said that the evidence was that Scottish young people needed "decent opportunities".

"The jobs market, like the housing market and even the benefit system is in many ways stacked against them," he said.

'We have undertaken surveys of young Scots and we have been astonished by the levels of despair they feel about their future.

"What young Scots need is more opportunities. '

TUC general secretary Frances O'Grady warned that under the scheme young people carry out unpaid community work would reduce the time they had to find paid employment.

SNP work and pensions spokesman Dr Eilidh Whiteford said young people should get "fair pay for a fair day's work", as she accused the Tories of targetting and "punishing" teens.

Labour said it would expected young people to take paid jobs under its "jobs guarantee" if they win in May.

But Mr Cameron said he had inherited a welfare system that was a "national disgrace", and that too many unemployed young people were sitting at home sinking into "depression and despair".

He said that the system too often trapped people in a lifetime on benefits, adding: ""People don't just live up to expectations - they live down to them too".

Mr Cameron's announcement came during a week in which the Tories hope to focus on their tough stance on welfare of the election.

The Prime MInister faced criticism at the weekend after it emerged he is considering stripping benefits from drink and drug addicts and the obese if they refuse treatment for their condition.