Business leaders have urged the Government to make provision for mental health first aid mandatory in the workplace.

More than 50 chief executives and leaders from companies such as WH Smith, Ford and Royal Mail have signed an open letter to Prime Minister Theresa May asking her to prioritise a manifesto pledge to update health and safety regulations.

The group calls for mental health to be given the same status as physical health at work, for both “economic and human” reasons.

The letter reads: “As an employer, we have a duty of care for our staff and whilst some employers are at the forefront of change, equalising their number of mental health first aiders with physical first aiders, we cannot afford to leave anyone behind.

“Cost cannot be a reason for objections because in the long run it is inevitable that making mental health first aid in the workplace mandatory will save money.

“Success will ensure that employees everywhere can access a trained staff member to receive initial support and guidance if they are dealing with a mental health issue at work.

“Success will ensure every employee has the right to a mentally healthy environment.

“It will also mean that we can finally break the stigma of mental health in the workplace.”

Prime Minister Theresa May Company bosses have written an open letter to Prime Minister Theresa May (Stefan Rousseau/PA)

Mental health issues are estimated to cost the UK economy almost £35 billion every year, while 15.4 million working days are lost to work-related stress, depression or anxiety.

Fionnuala Bonnar, chief operating officer of Mental Health First Aid (MHFA), which is leading the campaign, said the letter showed that business leaders recognise the need to support their employees’ mental health as much as their physical health.

“This is just one part of improving approaches to workplace mental health, but it represents an important step forward,” she said.

“Ensuring that first aid support is there for the millions of people who struggle with their mental health every year will make a big difference to how we all think about our health as a whole.”

Stephen Clarke, chief executive of WH Smith, added: “We are calling for this legislative change, alongside many other leading employers, as we firmly believe that everyone should have access to first aid support for their mental health regardless of where they work.”

Earlier this year, a study by the charity Mind revealed that almost half of UK workers have experienced a mental health problem at their current job.

A survey of more than 44,000 employees showed that only half of the 48% who had experienced poor mental health had talked to their employer about it.

Mind said the findings suggested as many as one in four workers is struggling in silence with problems such as anxiety, low mood and stress.

A Government spokesman said: “We have been clear that establishing parity between physical and mental health is a priority for this government, and we want to ensure that people with mental health conditions have the opportunity to progress in the workplace and achieve their potential.

“That’s exactly why we’re taking forward all 40 recommendations of the independent Stevenson Farmer Review of mental health and employers.

“The Health and Safety Executive will shortly be updating its First Aid guidance to help employers better understand the need to consider mental health alongside physical health.”