Remember the one about the little girl with the curl in the middle of her forehead? When she was good she was very, very good and when she was bad, she was horrid.

According to researchers, little girls today are not just horrid, they are the most sophisticated and manipulative bullies of all. Professor Dieter Wolke, of the University of Hertfordshire, is researching the extent of girls’ bullying at primary school.

He claims that unlike the obvious physical bullying usually carried out by boys, girls deploy much more sophisticated and complex methods - name-calling, whispering, spreading rumours and manipulating friendships.

He said: “Boys have been found to bully more then girls. But bullying by girls has long been under-estimated. If one considers excluding others from social relationships and the spreading of rumours about them as bullying, then girls may well be described as being as aggressive as boys.”

However, some children’s charities say it is more than the mental intimidation which is causing them serious concern. Anti-bullying charity Kidscape reports a 50 per cent increase in the number of calls concerning female-on-female violence over the past two years.

The charity’s assistant director, Gaby Shenton, said: “What we’re seeing and hearing is that bullying starts younger, that girl-on-girl violence is more common and that girl gangs are increasing. We are even getting calls about nursery school bullying, of the ostracising from gangs type.

“It’s a funny thing with the Spice Girl age group - for them the line between aggression and assertiveness is muddled and fuzzy. They want what they really, really want, but often don’t know where to draw the boundaries and how to handle it if they don’t get it.”

Mary McCloud, policy and research director at ChildLine, does not think girls are any nastier now than they have ever been: “I know lots of older women who had thoroughly miserable experiences at school, for all these reasons. But it’s true those tactics of not talking and whispering can be easily missed by teachers.”

Janet Eton, head of the Maple primary school in St Albans, makes a point of dealing with falling-outs and arguments as part of a school-wide behavioural management policy.

She says: “It’s important to keep a level head because little girls do fall out. But we’d be silly to ignore it. If you’re seven years old and you haven’t been invited to someone’s party, that’s devastating.

“Little girls place such stock on friendships and social groups, and that’s what they use to manipulate others. Things like hiding pencils, sending nasty notes under the desk or getting everyone else not to like someone are very common, but they can be difficult to detect.”