The government insists that the number of Neets is falling
Up to 18% of 16 and 17-year-olds are Neets, neither in employment, education or training, a study suggests.*
Official figures say such youths make up 7% of their age group in England.
An alternative analysis of the figures by the London School of Economics says up to 18% across the UK could spend most of their time doing nothing.
Children's Minister Beverley Hughes said: "We are making preparations now for every young person of 16 to 17 to be in education or training."
Official figures take into account any work or training by young people over several weeks - no matter how limited.
But the London School of Economics (LSE) researchers based their alternative analysis on what teenagers spend most of their time doing - which shows the number of Neets could be as high as 18% of 16 and 17-year-olds across the UK.
The government has put great effort into reducing Neets after Gordon Brown told 16 and 17-year-olds that "doing nothing" was not an option.
It says that there are 20,000 fewer Neets in 2008 than in the previous 12 months.
One young person, Helen Steward, told the BBC how she ended up as a Neet.
"Out of my whole year there was about 100 of us, and 30 to 40, like myself, were not in employment, further education or any kind of training, just not doing anything with their lives, just sitting at home doing nothing," she said.
Julia Neal of the Association of Teachers and Lecturers said that the curriculum was not giving young people the skills they needed.
"It's being too narrowly focused on tests and targets," the spokesperson added.
Richard Wainer, education and skills adviser to the CBI, argued that a significant proportion of younger people's potential was being wasted.
"If these young people don't have the skills and abilities that their potential employers are going to need, then they are not going to get jobs and that's going to lead to real social and economic problems," they said.
Ms Hughes said that the number of Neets was being reduced "through raising the participation age and through improving the quality the variety and the flexibility of education and training provision through diplomas and apprenticeships that will be available to them".
* Update 7 August 2008 : The LSE subsequently said such reports were "based on a misreading of the data".
It said the higher 18% figure came in part from counting students who were searching for part-time jobs (so were classified as "job seekers"). But it said students doing Saturday jobs should not be classified as "doing nothing".