For years we've known that people with mental health conditions die 10-20 years earlier on average than the general population.
Now, scientists have identified smoking as the "single largest factor" for this shocking difference in life expectancy.
“We know that people with a mental health condition are just as likely to want to stop smoking as other smokers. But this can be much harder if, for example, you are using smoking as a coping mechanism," Brian Dow, director of external affairs at Rethink Mental Illness commented.
"This is why people need specialised, longer term support. There is no quick fix for smoking and mental health. We need to work across mental and physical health services, and social care, to empower people to become smoke free."
The new report, created by Action on Smoking and Health (ASH) and endorsed by 27 health and mental health organisations, highlights that around one third of adult tobacco consumption is by people with a current mental health condition.
Smoking rates among people with mental health conditions are more than double that of the general population.
Commenting on the findings, Paul Farmer, chief executive of the mental health charity Mind, told The Huffington Post UK: "The relationship between smoking and mental ill health is an issue that we’ve long known about.
"Mental health services are on the path to becoming smoke-free by 2018, a move which will bring them in line with physical health services.
"For this process to be effective, however, it has to be done in the right way with proper support given to all those affected by the changes. We welcome the emphasis in the report on how to do this."
The study authors have also called for more specialist support to help people affected by mental illness quit smoking.
Paul Burstow, former Health Minister and chair of the Tavistock and Portman Mental Health Trust and chair of the report said: "It is time to challenge the idea that smoking amongst people with mental health conditions is either inevitable or intractable: it is not.
"With a determined and collective effort we can save millions of people from early death and avoid years of life being blighted by heart and lung diseases, stroke and cancer."
Smoking not only affects people’s health but also their wealth. New research conducted by the University of Nottingham as part of the report shows the contribution smoking is making to pushing people with a mental health condition into poverty.
It estimates that a million people with a "common mental health condition" are living in poverty and also smoke. Meanwhile a further 130,000 people are pushed into poverty once their spending on tobacco is taken into account.
Deborah Arnott, chief executive of ASH said: "The appalling gap in life expectancy between those with a mental health condition and the general population is unacceptable.
"Not only are high rates of smoking contributing to a widening gap in health, but also in wealth, with thousands of people pushed into poverty due to their expenditure on tobacco.
"To reverse these trends professionals in every part of the health and social care system must work together."