A trebling of the money spent on diverting people with mental health problems from prison would more than pay for itself in reduced crime, better health and lower costs to the criminal justice system, according to a study by the Sainsbury Centre for Mental Health.

It is more than 15 years since the government-commisioned Reed report called for a national scheme to keep out of court people with mental health problems who have committed crimes, but only one in five of such offenders are currently covered, the study said.