Young people are struggling to find work in the recession
Record numbers of young people are not in school, college or work in England, official figures show.
The ranks of 18-24-year-olds considered to be "Neets" - not in education, employment or training - has risen by more than 100,000 in the past year.
Chancellor Alistair Darling has insisted the government is doing all it can to avoid creating a "lost generation" of young people.
But the Tories accused ministers of making "empty promises".
The statistics show that in total, 835,000 18 to 24-year-olds are now Neets, up from 730,000 for the same quarter last year.
The figures, published by the Department for Children, Schools and Families, which are for the second quarter of 2009, also show a surge in the numbers of 16 to 18-year-olds considered Neets.
There are now 233,000 Neets in this age group, 13,000 more than the first quarter of 2009, when the figure stood at 220,000.
In the second quarter of 2008, 209,000 16 to 18-year-olds were Neets, 24,000 fewer than the same quarter this year.
Mr Darling, who is standing in for Gordon Brown during his holiday, said: "It's very important that we help young people get back into work or into training.
"At the end of last year we had record numbers of young people in education and training.
"We will, this September, be able to guarantee 16 and 17-year-olds education or training.
"And from the beginning of next year we will be able to guarantee people who have been out of work for a year either a job, training or further education.
"All of that is important so we don't repeat the mistakes that were made 20 years ago where a whole generation of people were lost.
"We are determined that will not happen again."
Mr Darling, who is visiting a job centre in Marylebone, central London, said he had predicted at the time of the Budget that unemployment would rise further this year.
He said: "It is important that we do everything we can, which is why we are spending over £5bn to get people back into work as quickly as possible."
Minister for apprenticeships Iain Wright admitted the economic downturn was having a "significant impact on young people".
But he insisted the new figures were seasonal estimates which "fluctuate" throughout the year and said the government had recently launched a national campaign to get more young people into jobs, education or apprenticeships.
He told BBC News: "We are not a government, frankly, that will walk on by and watch a lost generation of young people not get the skills and expertise and training that they need."
For the Conservatives, shadow universities and skills secretary David Willetts said: "It is very worrying that there is now a record number of 18 to 24-year-old Neets. More than one in six young people are now without a job or a place in education or training.
"Ministers have comprehensively failed to get a grip on this crisis. Young people don't need more empty promises or celebrity gimmicks. They need more apprenticeship opportunities, more postgraduate places and better careers advice."
TUC general secretary Brendan Barber said Britain could not afford "to lose another generation of young people to unemployment and underachievement".
He urged more firms to take on apprentices and the government to "ensure its guarantee of training or work for young people out of work continues to be well funded, as demand will be high".
"Neets are likely to have low skills and poor experience so the training and work on offer must be meaningful. Otherwise it will just be a stopgap before further unemployment."