Employers are far less likely to employ people with mental illnesses than those with physical ailments, a report shows.
People with mental health problems can find it hard to get a job
Just 20% of those with severe mental health problems have jobs, compared with 65% who have physical problems.
The government is launching an initiative urging employers to improve conditions for people with a mental health problem.
A spokesman for the Confederation of British Industry said the majority of businesses offered staff support.
It is estimated one in four people will suffer a mental illness at some point in their lives.
And even for those with more common types of mental illness, such as depression, only about half are competitively employed.
However, up to 90% of people with mental health problems want to work, compared to 52% of disabled people generally.
The voluntary standards, launched to coincide with World Mental Health Day, will also be used by public sector organisations, including local councils, government departments and hospitals.
The Disability Discrimination Act, which comes into force this December will require these bodies to end unlawful discrimination and promote equality of opportunity.
Health minister Rosie Winterton said: "Ignorance and stigma still surround the issue of mental ill-health and when someone does develop a problem, they often do not get the support they need from society to help them recover.
"We all have a role to play in helping to tackle this issue. Employers can help by raising awareness of mental health issues amongst staff, supporting those affected and combating discrimination against staff and customers.
"This is good for staff and good for employers, who we know will benefit from reduced staff turnover and sickness absences."
Work and Pensions Minister Lord Hunt said: "Work is important and beneficial to our physical and mental well-being.
"Because of this, it is essential that we remove the barriers that prevent people starting, returning to, or remaining in work."
A Confederation of British Industry (CBI) spokesman said: "Three quarters of companies already operate a stress management policy and 84% offer rehabilitation support when staff become ill.
"But employers, especially small firms, need more support and advice in helping employees with mental ill-health, so we welcome the Department of Health's promise to listen to business' needs and to develop commonsense guidance."
A growing number of parents think their children are depressed and are turning to a mental health charity for help.
Young Minds says one in five people who call their helpline are parents seeking advice about their children's depression.
Figures suggest that for every child who takes his or her own life, 50 more will try.