Mental health sees 300,000 people leave their jobs each year.

Up to 300,000 people with long-term mental health problems have to leave their jobs each year, a report says.

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". She is asking NHS England and the civil service to accept the report's recommendations.

Paul Farmer, co-author of the Thriving At Work report, said mental health was a taboo subject in many workplaces.

Mr Farmer, who is chief executive of mental health charity Mind, said: "Opportunities are missed to prevent poor mental health and ensure that employees who may be struggling get the support they need.

"In many instances employers simply don't understand the crucial role they can play, or know where to go for advice and support."

'My confidence is back'

The review makes 40 recommendations about how employers and the government can better support employees to remain at work, such as through creating an online wellbeing portal and using digital technology to support workers in the gig economy.

Companies are also being encouraged to include a section on employee mental health in their annual reports. Currently only 11% of companies do this, the report found.

Postwoman Caroline Benson was diagnosed with depression 17 years ago. She says she has received a lot of support at work including access to counselling.

Ms Benson told BBC Radio 5 live: "It means I can go to them [her line manager] straight away, as soon as I'm struggling then my recovery from that bout is much quicker.

"It does make life a lot easier to know that I can come to work and be supported because work really is the best place for me to be.

"I need that support and structure around me to give me that positive outlook on life."

One employer the report praised is the insurer Aviva.

James Tringham has worked for them for seven years. He said the company helped him get his life back on track after it was crippled by his bipolar disorder:

"In 2009 I'd reached crisis point with my mental health, and I gave up my career as a solicitor.

"I was unable to work for over a year - the prospect of returning to work was just so frightening and not something that I could imagine."

Eventually he got a job in the insurer's contact centre. He said: "They gave me a way back into employment and I have worked my way back up.

"Aviva have been brilliant in supporting me to manage my mental health at work, and have given me my confidence back.

"There's an understanding, which means little things like adjusting my workload when I'm feeling on the low side can really help. And the staff - both officially and unofficially - form a great support network."