If you thought a little extra flesh might help to secure that promotion, you couldn't be more wrong.

According to Elisabeth Squires, author of Boobs: A Guide to Your Girls, there are strict rules on cleavage in the workplace.Having recently commissioned a study which established that women were increasingly showing more cleavage at work, Squires says that a plunging neckline and short skirt can be offputting to colleagues as well as appearing less professional.

So what is acceptable? Miss Squires suggests that two or three inches of cleavage at work may be tolerated, but plunge any further and you could be hampering your promotion prospects.

She told the Daily Mail: "I don't think women are stupid, I just don't think anyone knows the rules.

"Women understand the power of breasts in general, but they don't understand the power of their own."

The study she commissioned asked men to look at images of women in the workplace wearing a variety of outfits and bra sizes. Those picked as the most professional were the discreetly dressed ladies with medium-sized breasts.

But whatever your breast size and whatever your job, Miss Squires, who has been writing about breasts for 20 years, has one last piece of advice: "If cleavage isn't in your job description, don't write it in."