The Chancellor used his Spring Statement in March to announce a review into how to help the UK's least productive businesses catch up with others.

Yet the secret to greater output for Britain's companies may not lie in analysing spreadsheets or improving technology but in helping the bosses of small firms support staff suffering from mental health problems.

Mental health accounts for 40% of absenteeism people across the country, according to Lord Layard, a leading labour economist at the London School of Economics.

In 2007, the CBI and AXA estimated the cost of absence to employers in the UK is more than £13 billion a year.

Yet Lord Layard had a warning for executives and bosses gathered to hear his speech at the Wellbeing Symposium, a conference on health and happiness at work, held at the Ashford International Hotel in February.

"We have got to train line managers to notice the condition," he said.

"If a person goes off sick, it's not just a job for HR. That shows you don't take it seriously if you delegate it to HR.

"In any workforce some people really struggle with mental health problems and it's important that managers have the knowledge and confidence to help people with these problems.

"One in seven people working with you will be diagnosed as suffering from depressive or anxiety disorder. This increases absenteeism and reduces productivity."

Lord Layard admitted he was "preaching to the converted" at the conference attended by 240 people, now in its sixth year.

The event, run by Marden-based Wellbeing People and Maidstone-based Pillory Barn, hosted a range of speakers including Paralympian and former Great Britain wheelchair rugby captain Steve Brown.

Vidya Krishna, a GP in Tenterden who also works at the Pilgrims Hospice in Ashford, was in the audience.

She said: "If your workforce are happy you're going to be able to get an impact in terms of what you're trying to achieve in the workplace.

"It's not focused on as much as it should be. If you're happy in the workforce you will be able to perform better."

"It's a massive issue," said Leo Bunyard, who runs the Maidstone Yoga Centre.

"Businesses like Wellbeing People are getting that information out to wider society but it's a shame because people here are converted to that viewpoint.

"What needs to happen is that small recruitment agencies in the City, for example, need to be using these sorts of techniques because it will make their workforce more productive and happy.

"The economy of the county will benefit.

"Quite often people are very secretive about suffering with mental health problems.

"People don't say they suffer from depression in the workplace because they are concerned their line manager will use techniques to get rid of them because they will not want someone likely to take time off."