A new report on mental health in the workplace, Thriving at Work, has prompted a swift response from Government and business groups.
The independent review has found that 300,000 people a year are leaving their jobs each year due to mental illness - costing employers up to £42 billion annually.
The report, from Lord Dennis Stevenson, a long-time campaigner for greater understanding and treatment of mental illness, and Paul Farmer, ceo of Mind, includes 40 recommendations for the public and private sector.
Prime minister Theresa May said: "We need to take action. That's why I am immediately asking NHS England and the Civil Service - which together employ more than two million people - to accept the recommendations that apply to them. With so many of our leading businesses leading the way in this area … I am sure that the private sector will follow suit."
The prime minister has written to key business groups, including the CBI, the Institute of Directors (IoD) and Federation of Small Businesses (FSB) to encourage them to implement the recommendations in their organisations and across their networks.
Mike Cherry, FSB chairman, said: "We welcome the efforts of the reviewers in attempting to understand the small business perspective … Owning and running a business brings with it different challenges and pressures that can impact an individual's mental health.
"Small businesses and the self-employed are keen to work with Government and others to meet that challenge. There is a collective responsibility shared by Government, business owners and each of us as individuals to work together to destigmatise mental health and create an open environment where we can all talk about and take care of each other's mental health."
Stephen Martin, IoD director general, said: "This report adds some much-needed Government backing to the calls for more open conversations about mental health at work. The review … shows that mental health is not just a moral issue, but a business one too.
"Official statistics suggest that 127 million hours of work were lost in 2015 due to mental health related absence. Even when poor mental health isn't forcing individuals to take time off work, it's affecting their performance in work."
There are many resources available to employers to help them tackle mental health in the workplace, including an IoD portal on Mental Health in the Workplace, an FSB hub, Wellbeing in Small Business and new guidance for employers from Acas.