It also claims poor mental health costs the UK economy up to £99bn each year.
Prime Minister Theresa May, who commissioned the report, said it showed "we need to take action". The UK civil service has agreed to take on the report's recommendations.
Paul Farmer, co-author of the Thriving At Work report, said mental health was a taboo subject in many workplaces.
- Can you talk about mental health at work?
- The illness that affects one in six of us
- Mental health staff on stress leave up 22%
"In many instances employers simply don't understand the crucial role they can play, or know where to go for advice and support." Continue reading.
Originally posted on BBC Health.