There are now 1.24 million people aged between 15 and 24 who are neither in education, work or in a training scheme — a 15 per cent increase on 1997. The rise has been particuarly rapid for 16 to 17-year-olds and men, both up by almost a third.

The figures, from the Office for National Statistics, are an embarrassment for the Government, which has spent billions of pounds helping disadvantaged young people to stay on at school, train and get a job.

Both Labour and Conservatives yesterday placed the blame for social breakdown at the door of errant fathers, putting the issue of social justice at the heart of the next election. Iain Duncan Smith, the former Conservative leader, will unveil today his 300,000-word report blaming the breakdown of traditional families for poverty, school failure and crime. He will blame men rather than single mothers, a traditional Tory target, for the failure.

David Willetts, the Shadow Education Secretary, who uncovered the figures, said: “It shows an extraordinary failure of government policy. Even if you put in large amounts of money, if you haven’t got the basic policies right, you won’t get the results. For kids from the most deprived backgrounds, things are getting worse.”

Rob Cope, a spokesman for The Prince’s Trust, said that the figures confirmed the organisation’s experience of working with deprived youngsters.

“If you look at the most deprived, in relative terms they’re becoming worse off. They leave school with no qualifications, end up in prison, and the cycle of deprivation continues. Those at the very margins are increasingly disengaged from the rest of society — they see all these government schemes, but say they have seen it all before.” Many of the young men not in education, employment or training resort to criminal activity, both to occupy themselves and to make money, with a high proportion ending up in prison.

There is also a strong social divide, with young people whose parents are manual workers twice as likely to be out of education, employment or training as those whose parents are professionals.

The study suggests that the rise in young people doing nothing is caused by failures in the school system, in vocational qualifications, and in the flagship New Deal for young people, launched with much fanfare just after Labour was elected.

Nearly 30,000 people a year leave school without any qualifications, while nearly a third who leave school with fewer than five GCSEs end up out of work, unemployed and out of training by the time they are 18. Independent research suggests that some of the post-school vocational qualifications that the Government launched are a waste of time, bringing no benefits to those who take them. The New Deal programme is performing increasingly poorly, with the number of young people who find jobs on leaving the programme halving from 60.8 per cent in 1998 to 34.6 per cent now. Nearly half of those who join the scheme end up back on benefits within a year.

Phil Hope, the Skills Minister, said: “The true story is that more than 1.5 million 16 to 18-year-olds are in education and training — the highest number ever. We have made excellent progress — nine in ten of all 16-year-olds are in education and training.”

Jim Murphy, the Welfare Reform Minister, said: “The New Deal is a great success, so far helping over 1.6 million people into work.”

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