Workers in London are suffering the most, with 40% saying they feel as though their employers do not provide enough support for their mental health.
Around 43% said they would start looking for a new job if their employers do not do more to support their mental wellbeing, according to online healthcare provider Lime.
The stark numbers come as bosses try to incentivise employees to end the practice of working from home, although several big name businesses have implemented hybrid working.
Almost one in five surveyed said they are concerned about their stress being visible to others, while 26% said they do not think they are coping.
Over a third feel the same way about everyday life, leading to 40% of those questioned saying they feel less resilient generally now than they did before the pandemic.
Young people are bearing the brunt of these challenges, with 43% of women aged 16-24 and 49% of men aged 16-24 feeling less resilient now than they did before the pandemic.
Women also feel they are under more pressure than male colleagues to put on a brave face, with younger women feeling the pressure the most, Lime said.
Only 16% of respondents said they feel their mental health is very well supported at work, despite businesses claiming the pandemic has led them to increase awareness and support for employees.
Workers said their mental health would improve with employers being more mindful about workload and work/life balance, greater flexibility in working hours, time out to deal with personal commitments, and mental health days off work.
Shaun Williams, chief executive and founder of Lime, said: “The past 18 months has had a huge impact on people’s lives, including on their mental health and resilience.
“The long-term repercussions of the pandemic are likely to be felt for years to come, and it’s important we act now to be aware of and prioritise both our own mental health and that of those around us.”
He added: “We know that employers have a lot on their plates and each workforce will require unique approaches for tackling mental health challenges.
“But there are plenty of simple and affordable avenues for doing so. It’s only by drawing attention to and prioritising mental health in the workplace that we can support one another to be as healthy, resilient, happy and productive as possible.”