Drug education and prevention services for some of England's most vulnerable children are facing "disastrous" funding cuts, a charity has claimed.
Hard drugs use among youngsters has remained stable since 2001
Government funding, mainly for prevention work in schools and among excluded pupils, is being reduced by £6.6m or 10% in 2007-08.
Children with drug and alcohol problems or those at risk of developing them would be hardest hit, says DrugScope.
The Home Office said drugs misuse had fallen by a fifth since 2000.
DrugScope chief executive Martin Barnes said the cuts would be "disastrous for local services" and were "extraordinary" given that tackling drug and alcohol misuse among young people was a government priority.
"Services are being cut back and experienced qualified staff being made redundant or moved.
"Local grant allocations were announced by the Home Office in late February but the cut in funding and its severity has only just come to light," he said.
The kinds of services at risk include those working with young offenders and pupil referral units, where a child may be using or at risk of substance misuse or it is a problem in the family.
Others deliver drug education in schools or work with them on drug-related incidents.
Mr Barnes said DrugScope had been alerted following calls from drug workers alarmed about the impact on services.
"Officials say that budgets for adult drug treatment can be used to make up shortfalls in young people's treatment, but this is simply robbing Peter to pay Paul.
"Adult services have demanding targets to meet and in some areas funding for adult treatment has been reduced," he added.
A Home Office spokeswoman confirmed the funds were being cut but said the government was committed to tackling young people's substance misuse.
These grants were one of a range of ways through which it tackled drugs, she said.
"The school survey, published last week, showed that drug misuse among young people had fallen in 2006 compared to the previous year.
"We have invested £7.5bn in tackling drugs since 2001 and drug misuse has fallen by 21% in the last seven years.
"We will continue to tackle drugs through education, enforcement and treatment."
Recent figures show drug use among 11 to 15-year-olds has fallen recently - but the number of youngsters using more serious drugs has remained constant since 2001.
Figures for 2006 suggest 29% of 15-year-olds had taken a drug in the past year, with 4.3% of 11-15-year-olds saying they had taken a Class A drug.
Drug services for young people are set to face further uncertainty as in 2008 responsibility for them passes to local authorities and the grants will no longer be ring-fenced.