Employers will have to protect their staff from stress - or risk legal action, a watchdog has warned.
The code says companies should protect staff from excess stress
The Health and Safety Executive has launched a six-point code which firms must abide by.
They must support their employees and ensure they do not feel overly pressured in their roles.
Companies will be assessed to see if they have reduced stress to manageable levels.
If fewer than 65 to 85% of all staff feel each standard has been met, the company will fail its assessment.
There is a difference between the buzz people get from doing a busy and challenging job and an unreasonable pressure which can harm health
Bill Callaghan, Health and Safety Commission
The code was piloted in 24 companies ranging from academic institutions to a supermarket chain - and their positive initial comments have fuelled plans to make it more available to others.
The HSE believes the "stress code" will make it easier for employees to bring actions against firms, and will give its inspectors something to measure firms' performance against.
Employees can already sue their companies for causing them unnecessary stress at work under the Health and Safety at Work Act.
The six stress tests
Demands - 85% of employees must say they can cope with the demands of their job
Control - 85% must feel they have an adequate say over their job
Support - 85% must say they have the back-up they need
Relationships - 65% must say they do not have to face unacceptable behaviour such as bullying
Role - 65% must say they understand their roles and responsibilities
Change - 65% must say they are involved in organisational change
But cases can be difficult to prove, and the HSE has not brought any prosecutions on these grounds.
Up to 13.4m days a year are lost due to stress at work.
Bill Callaghan, chair of the Health and Safety Commission, said: "We know that there is considerable pressure in the modern workplace.
"But there is a difference between the buzz people get from doing a busy and challenging job and an unreasonable pressure which can harm health, lead to absence and put additional strain on their colleagues trying to cope in an even more pressured environment.
"Stress is on everyone's lips and business people are becoming aware of just how costly not dealing with this problem can be."
Cary Cooper, Bupa professor of organisational psychology and health at Umist in Manchester, told BBC News Online: "This is a very laudable idea.
"The research is quite conclusive that stress does cause ill health in the workforce.
"The HSE has looked at the data and looked at the factors in the workplace which cause the problems."
Professor Cooper added: "This will help and encourage employers to act because the code is telling them what the causes of stress are."
He said that because the HSE had spelt out six main causes of stress, employers would not be able to defend legal action by saying they were not aware of a problem.