The number of pupils with mental health disorders is set to double to a point where a fifth of five to 15-year-olds are affected, a government adviser has warned.

Professor Barry Carpenter, who chaired a major national inquiry into mental health, told The TES that the economic downturn would play a part in children’s emotional problems.

The Oxford University academic, who advises the Prime Minister, also argues that official figures do not take into account the high incidence of mental health problems among pupils with special needs.

The latest Office for National Statistics survey, undertaken in 2004, showed that 10 per cent of children had mental health problems.

Professor Carpenter said: “If you combine into that figure what we know about children with special needs - for example, for every five children with special needs we know that three will have a mental health problem - I think overall the one in 10 is going to creep up as you get more vulnerable children and as homes start to feel the economic recession.”

He said the health and well-being of some children could be damaged as their parents were made redundant or had their salaries cut.

Asked to quantify the rise in five to 15-year-olds with mental health problems, Professor Carpenter said: “It is 1 in 10 at the moment. I think over the next 10 years we will see it move to two in 10.”

His warning came as a Prince’s Trust survey of 16 to 25-year-olds this week found that one in 10 believed life was not worth living. The poll of more than 2,000 showed that more than a quarter of them felt depressed.

As The TES revealed last month, ministers already fear the recession will lead to poorer pupil behaviour. Jim Knight, the schools minister, said he thought schools would have to manage the fall-out from families struggling with redundancies and mortgage arrears.

A Department for Children, Schools and Families spokesman said: “In a survey of 110,000 pupils last year, 93 per cent of children said they felt happy about life.

“But we know childhood isn’t good for every child and we will continue to focus on the problems that exist for some.”

Professor Carpenter chaired the National Inquiry into the Mental Health of Young People with Learning Disabilities in 2002, supported by the Department of Health and the Department for Education, and now sits on the Prime Minister’s Standing Commission on Carers.