Mental health patients smoke more than three times as much as the general population, a Public Health England (PHE) and NHS survey of 105 care units suggests.

Smoking can increase depression and anxiety and reduce the effectiveness of medication by up to 50 per cent, experts warn.

PHE wants all mental-health hospitals to be smoke-free zones.

But smokers’ rights group Forest says patients in mental health units should have the same freedom to smoke as the general public.

The PHE survey suggests 64 per cent of mental-health patients are addicted to tobacco – compared with 18 per cent of the general population, although nine of the units are already completely smoke-free.

A separate study published in the Lancet recently found that 50 per cent of those suffering from serious mental ailments such as schizophrenia and other psychoses smoke cigarettes and are unlikely to quit easily, as compared to 15.5 per cent of people without such conditions.

It also points out that in some people with schizophrenia, nicotine use might be a form of self-medication used to attenuate the negative symptoms of their disorder, improve their cognitive performance, or reduce the severity of the side effects of their antipsychotic medication.

The PHE survey said experts believe smoking is the main reason mental-health patients have a life expectancy that is 10 to 20 years lower.

Kevin Fenton, PHE national director of health and wellbeing said the organisation wanted to “reduce the unacceptable inequalities in health experienced by people living with mental-health problems”.

Mary Yates, matron of London’s Maudsley Hospital said there was growing evidence that smoking cessation enhances people’s mental wellbeing.

Ms Yates added: “People who are able to successfully give up smoking feel less anxious, have improvements in their moods, have increased self-confidence, and begin to feel that they are able to tackle a lot more in life.”

But Simon Clark, director of the smokers’ group Forest, said: “Smoking is not just about health, although many smokers believe it helps reduce anxiety and stress. If some mental health patients enjoy smoking why should they be denied that pleasure?

“What PHE is proposing is discrimination. It will target unfairly a group of people who, being dependent on others, has little alternative other than to comply.”