More than 80 per cent of the country's psychiatric wards are failing to enforce the smoking ban, says a report to be published tomorrow.
Staff shortages, a lack of safe outdoor space and insufficient training in quitting techniques means staff have had little success in stopping patients smoking indoors, says research by the Mental Health Foundation.
Around 70 per cent of people with severe mental health problems smoke cigarettes, but those admitted to hospital under section are often unable to leave the confines of the ward without special permission and accompanied by a staff member.
The ban – in force since 1 July 2008, a year later than elsewhere to enable hospitals to make provision – has led to secret smoking among patients, according to the foundation, which is calling for a review of the ban's impact.
Simon Lawton-Smith, head of policy at the Mental Health Foundation, said: "We need legal guidance... there is no point in having a law which is clearly being flouted on a daily basis."
Ralph Hill, 60, from north Essex, who has bipolar disorder, said: "Yes, smokers are offered help to stop, but many are too ill to cope with giving up at the same time as being sectioned."