Getting out of bed on the wrong side is a common enough problem. Most people endure the odd 'off day' at work when cracking a smile becomes mission impossible and colleagues gingerly tiptoe around your desk.

But spare a thought for employees at a German computer firm who have to smile from nine to five - or face the sack.

Manager of Nutzwerk, Thomas Kuwatsch, has enforced a 'happiness clause' in the office where whinging is banned and moody workers are encouraged to stay at home rather than inflict their grumpiness on colleagues.

"We made the ban on moaning and grumpiness at work official after one female employee refused to subscribe to the company's philosophy of always smiling," Mr Kuwatsch says. "She used to moan so much that other employees complained about her complaining."

An unhappy workforce is certainly no laughing matter. An astounding 12.8 million working days a year are lost to work-related stress in the UK, according to mental health charity, Mind. More than half of workers questioned (58 per cent) also complained of 'job stress'.

Grumpiness at work is a bigger problem than a fleeting attack of the Monday morning blues. Short-fused temper tantrums and dishing out the silent treatment to colleagues can generate ill-feeling and setbacks in the workplace.

"Mood is a powerful factor in organisations," says chartered work psychologist Dr Joan Harvey. "There are lots of things at work that can make you grumpy, like having a disagreement with a colleague or being put down by your boss, which can immediately affect your performance."

Manager Mr Kuwatsch may think his quirky happiness clause has his staff productivity covered but Dr Harvey says that mood is impossible to predict. "Mood is not stable. You can go to work in a bad mood and be in a good mood by lunchtime, or go to work feeling great and come home in a foul frame of mind. Mood is terribly transient and very difficult to control."

"Mood is also associated very strongly with stress so if you're in a bad mood you're likely to experience some symptoms of stress - at the very least tension across your shoulders or a headache."

INFECTIOUS MOODS

Forget the flu virus spreading around your office, all the vitamin C in the world won't prevent you from catching the moody bug if it takes over your colleagues.

"Other people can affect your mood in the workplace and vice versa," says Harvey.

"When you're in a bad mood at work, other people pick up on that vibe and it can cause a bad atmosphere. As individuals we respond to social signals so if you at smile at someone, they smile back. A bad mood will have the same affect on your colleagues - it doesn't make you feel good, or the people around you."

If you have a work colleague that seemingly gets out of their bed on the wrong side every morning, Harvey says there are tactful ways to deal with the problem.

"Don't confront colleagues about being grumpy as you may aggravate the situation further and possibly upset them even more," she advises.

"The best way of dealing with grumpy colleagues it to try and cheer them up. If they're being very self-indulgent with their moodiness or acting very withdrawn, there isn't a lot you can do. Let them work through their own problems."

MOVING ON FROM MOODINESS

If going to work fills you with dread in the morning or making a cup of tea for a colleague causes your head to boil like the kettle, it's most likely that work-related issues are the reason behind your moods.

Harvey says constant grumpy behaviour could be a sign of work dissatisfaction :''If your moodiness at work is prolonged, it may be an indication that you are unhappy in your job.

"You're either unhappy with your colleagues, boss, work or commuting - and something needs to change."

But if the problem is not work-related, Harvey suggests it's best to be open about your frustrations so that people don't mistake your mood for a personal gripe.

"It often helps to explain to people why you are in a bad mood and vent your frustrations - it can often help to lift the mood," she says.

"Everybody can have a personal plan that can help them get out of a grumpy mood so it's a good idea to find a tactic that works for you."