The cost of mental health services is expected to rise by 45 per cent over the next 20 years, the King’s Fund has predicted.

But in its long-awaited report on the future funding of mental health services, it says the NHS should not be expected to fund the increased cost alone.

The government must move money from other departments that reap the benefits, such as the Department for Work and Pensions, it says.

The King’s Fund predicts that the growing and ageing population will increase the number of people with mental health problems by 1.2 million by 2026.

Dementia already accounts for 66 per cent of mental health costs and this will rise to 73 per cent.

Its report, Paying the Price: the cost of mental health care in England, projections to 2026, says half of people with anxiety disorders and a third of those with depression are not in contact with services, and 46 per cent of those who are do not receive any therapy.

It recommends primary care trusts commission more evidence based and cost-effective interventions. This would reduce the£26.1bn it costs each year when people with mental illness are not able to work.

The report also recommends crisis services for schizophrenia and bipolar disorder are expanded because they reduce inpatient bed days and save money.

Early detection and treatment of dementia should be “a priority” because of the extra care the growing number of patients will require, the report says.

The National Institute for Health and Clinical Excellence rejected Aricept for mild dementia, saying that at£2.50 a day it was not cost-effective.

Senior lecturer at the Institute of Psychiatry Paul McCrone, a co-author of the report, said NICE was mandated to look only at the impact of treatments on NHS finances, so its remit needed to be widened. “If they took into account more fully the impact on carers for example, then maybe the drugs are cost-effective.”

For more coverage, see this week’s leader and Michael White’s column.