British businesses are badly under-estimating the extent to which their workers and managers are suffering from stress, anxiety, depression and other forms of mental ill health, a disability charity has warned.
This complacency is costing business more than £9 billion a year in lost time, the Shaw Trust has said.
Its research has found that there is a widespread discrimination and prejudice in the workplace against employees who have taken time off work because of a mental health condition.
It was also revealed that most UK businesses do not have effective policies or provision to manage their employees' mental health.
There also continues to be a lack of understanding about mental health in the workplace and a stigma attached to mental health problems, it found.
Yet that most company directors also recognise industry needs help to deal with the issues.
The research found that most company directors under-estimated the likely incidence of mental ill health among employees and colleagues, or the implications of this for their business.
One in three directors could not mention any specific condition, such as stress, depression or anxiety, when asked what disorders they thought of in connection with mental health in the workplace.
One in five employers admitted to believing that employees who had been off work with stress, depression or some form of mental ill health for more than a few weeks were unlikely ever to recover. One in three thought they were less reliable.
A similar number said negative attitudes from co-workers were a major barrier to employing people with any form of mental health problems.
Around half thought organisations took significant risks when employing such workers, or keeping them, in public or client facing roles.
There was no significant difference in responses between small businesses and large employers, it also reported.
When it came to employee attitudes, around three in every ten employees would experience stress, depression or some other form of mental ill health in any year, according to figures from the mental health charity Mind.
Yet only around one in six employers recognised that this national average was likely to apply to their people.
Only about 3 per cent of all directors thought their company had a policy that was effective to deal with stress and mental ill health in the workplace. Eight out of ten employees said their company has no policy at all.
And seven out of 10 employees admitted to not knowing enough about their legal position and obligations relating to mental health, said the trust.
Tim Cooper, managing director of the Shaw Trust said: "Mental health is probably the last workplace taboo. Society has confronted discrimination on the basis of age, gender, race, sexual orientation and religion, but there is a worrying lack of understanding about mental health and it is not often openly discussed.
"There is still workplace discrimination towards people who have suffered mental ill health, although it may not be deliberate or conscious. It wastes ability, talent and skills and spoils lives," he added.