Researchers believe the true figures could be even worse because bosses failed to recognise mental health problems and employees didn’t want to record them.

It also says that many people would rather struggle on coping with stress or depression than admit they have a problem.

The study was carried out on behalf of the Shaw Trust, a national employment charity.

The £556 million was on top of other costs to employers, such as National Insurance contributions, lost productivity or the extra cost of employing temporary staff to replace the absent worker.

Tim Cooper, Shaw Trust managing director, warned employers the worst thing they could do was ignore the problem.

“Businesses are putting their bottom line in danger, not only by losing valuable workers, but also by putting themselves at risk of costly lawsuits for discrimination,” he said.

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