The Coca-Cola Co has defended itself over criticism that a UK advert for its Glaceau Vitamin Water brand encourages workers to fake illness.

The wording on packs of the Coca-Cola-owned water brand in the UK states: "If you've had to use sick days because you've actually been sick, then you're seriously missing out." It adds: "The trick is to stay perky and use sick days to just, not go in."

The Forum of Private Business (FPB) said this week that it was “disappointing” that a multi-national company like Coca-Cola is condoning “bogus sickness absence in this way”.

“Employee ‘sickies’ can cause huge problems for small firms and anything which encourages workers to call in sick without good reason is likely to cause consternation among small business owners,” the FPB added. “Coca-Cola may see this a bit of a joke but I doubt the company would find it quite so funny if its own employees followed the advice on its labels.”

However, Coca Cola said the line is “clearly a tongue-in-cheek reference”, in keeping with the tone the brand has adopted with consumers since its launch.

“This is just one of a series of fictional stories on the back of pack which help demonstrate the brand's personality," the company said. "We are not seriously suggesting people should call in sick when they are not and on pack we state “taking a sickie is very, very naughty"."

Coca-Cola added that feedback since it launched the brand in 2008 has shown that its consumers “appreciate the irreverence of the brand”.

In October last year, Coca Cola was forced to scrap three poster adverts for its Vitaminwater drinks brand after the UK's advertising watchdog ruled that they may mislead consumers.