By Emma Wilkinson
Health reporter, BBC News
Access to child therapy services is currently patchy
Children's mental health services need an extra 1,000 therapists to help them cope with demand, an influential government adviser has warned.
Lord Layard, whose advice prompted a recent £173m investment in adult therapists, said training of child specialists should start in 2010.
Over a three-year period, his proposals would cost £35m, his report said.
A Department of Health spokesman said officials would be meeting with Lord Layard to discuss his proposals.
Experts welcomed them and said providing therapy early when needed could prevent problems in later life.
Around 10% of children have diagnosable mental health problems, said Lord Layard, who is emeritus professor of economics at the London School of Economics.
But only a quarter of them have seen a mental health professional of any kind in the past year.
This "unsatisfactory" state of affairs has serious long-term consequences, he said in his report.
To address the shortfall, 200 child therapists need to be trained every year for five years, he has calculated.
The additional workforce could be drawn from those who already have experience working with distressed children.
Any additional costs are relatively small compared with the NHS budget for mental health, which was £9.1bn in 2006/07, he added.
"We urge that this proposal be approved within the forthcoming comprehensive spending review and started, if possible, in October 2010," the report concludes.
Recommendations from Lord Layard prompted the government to invest heavily in psychological therapists for adults after he calculated the cost saving through people returning to work.
Dr Tim Kendall, joint chairman of the National Collaborating Centre for Mental Health, said the investment in children's therapists was long overdue.
"I did a series of systematic reviews of cognitive behaviour therapy for all childhood disorders including depression, anxiety, ADHD, and there's no doubt that it is really useful and has a positive effect for kids," he said.
Professor David Cottrell, an expert in child and adolescent psychiatry at the University of Leeds, said there was also evidence emerging that parental training programmes were effective in helping children with some mental health issues.
"One problem with child and adolescent mental health services is often the expenditure is in the health service but the savings are in other services such as education or the police and youth offending."
Sarah Brennan, chief executive of the Young Minds charity, said a transformation in children's services was required.
"The call for training in proper mental health assessments is essential," she said.
"We often hear from young people of the trauma associated with repeated assessments.
"In three weeks one young person saw 17 different mental health professionals, all of whom she to had to retell her story.
"The costs outlined in Layard's recommendations are a fraction of the NHS mental health budget and would be more than repaid in savings in future care and social costs."