Two-fifths (39%) of employees' organisations do not offer mental health support at work, according to research by employee services organisation Personal Group.
The survey of 1,089 employees, which took place in September and October 2018, also found that two-thirds (66%) of respondents feel that their employer does not offer enough support for mental health in the workplace.
While 80% of employees told the survey they had noticed an overall increase in awareness of mental health generally in the UK, 62% said they had noticed no corresponding change in the levels of awareness in their own workplaces.
Rebekah Tapping (pictured), group HR director at Personal Group, said: "It is surprising, not to mention a real shame, that such a large number of employees still feel there isn't enough mental health support available in the workplace, especially surprising as the topic has significantly increased awareness in recent years."
Although 64% of respondents said they believe they could provide support for someone struggling with a mental illness, 58% said they would still prefer to be provided with mental health awareness training by their employer, to help develop their understanding and skills.
Among the respondents, 28% of men wanted their organisation to offer mental health support via an employee helpline, compared with 23% of women.
Three-fifths (60%) of respondents said they thought they would be able to notice the signs of someone suffering from a mental health problem, while 36% said they were unsure.
Tapping said: "It is more important than ever that business leaders and decision makers break the culture of stigma and silence around mental health and start making it a management priority and ensuring that a range of support is available for those who need it."