Three quarters of people with mental illnesses are not getting treatment, experts warn.
The NHS is failing millions of people who have depression, behavioural problems or anxiety because it spends just 13 per cent of its budget on mental health, says the London School of Economics.
Simple, cost-effective therapies could save hundreds of millions of pounds, the researchers add.
Professor Lord Layard of the LSE Centre for Economic Performance said mental health is so widespread it should have a special cabinet minister dealing with it.
He said: ‘If local NHS commissioners want to improve their budgets, they should all be expanding their provision of psychological therapy.
‘It will save them so much on their physical healthcare budgets that the net cost will be little or nothing.
‘Mental health is so central to the health of individuals and of society that it needs its own cabinet minister.’
Mental health charities welcomed the report.
Mental Health Foundation chief executive Dr Andrew McCulloch added: ‘The report underlines the fact that mental health remains a poor relation to physical health despite the major links between depression, diabetes and heart disease, for example.
‘We have to tackle a situation where only 25 per cent of people with common forms of mental illness are receiving treatment and where there is massive under-investment in mental health research.’