One-quarter of teenagers find themselves not in employment education or training (Neet) at some point, according to a report by the Audit Commission.
The research found the problem with 16-18-year-old Neets was much worse than previously feared.
The government has estimated that one in 10 young people is a Neet. But the Audit Commission has found this figure is closer to one in four, and a 10th of those – 85,000 young people nationally – have been inactive for six months or longer.
The Audit Commission, which analysed the records of 24,000 young people in 10 areas of England, warned Neets are at risk of falling into long-term unemployment, poor health and even a life of crime, the Daily Telegraph has reported.
Michael O’Higgins, chairman of the Audit Commission, said: “Young people should be the future, but tens of thousands are at risk.
“After age 18, they could drift into unemployed, unqualified and untrained adulthood. This core group of young people, out of work and education for six months or more, is often overlooked.
“While there is £8.67bn set aside for 16-19 learning and support, most of it rarely reaches these more disadvantaged teens who need more intensive support.”
He added: “The stark truth is, without better targeted help, there is a huge price to be paid by these individuals, by their children, and by society.”
The study also revealed Neet levels in some areas were as high as 14%, although they average 9.2% across the country.
It is estimated a single Neet “cohort” will cost taxpayers £13bn over their lifetimes in welfare payments, criminal justice expenditure and lost tax revenue.