Joan Smith: Are devil girls really on the rampage?

It's a bit like watching the trailer for that hilarious sci-fi classic, Attack of the 50 Ft Woman, which thrilled audiences with the news that "the most grotesque monstrosity of all" was on the loose. This time, to be fair, the monsters are the same size as the rest of us but the really terrible thing about them, like the deranged avenger in that Fifties movie, is their sex.

"Girls are killing guys", a young man declared on yesterday morning's Today programme. "They think girls are angels and boys are devils, but sometimes girls can be the devil", said a terrified 14-year-old girl.

Ah, those devil girls: it could only be August, a month when killer sharks are spotted off Cornwall, baby tigers pop through cat flaps and David Cameron promises to repeal the Human Rights Act. To be honest, I'm kicking myself; when last week's big news story was the danger of confronting teenage boys about their anti-social behaviour, I should have known that "bad girls" – as Jenni Murray memorably called them on Woman's Hour a couple of months ago – would not be far behind. It's happened so often that on this occasion I can't even be bothered to misquote Kipling on the female of the species being deadlier than the male.

It's one of the iron rules of a misogynistic culture that any story about men or boys behaving badly has to be followed by a "balancing" piece in which someone points out that women and girls are pretty awful too. This is not to suggest I don't think there's a problem with adolescent boys and anti-social behaviour, especially after two tragic deaths in the space of a week, but it's important to keep things in proportion; not every boy aged between 13 and 18 is in a gang, carrying a knife or gun and looking for a confrontation to prove how tough he is.

The number of young men injured and killed in this kind of violence is unacceptable but the solution – teaching vulnerable boys to have a secure identity which isn't based on violence – is pretty obvious. At the same time, as long as this kind of brittle, showy masculinity continues to be valorised in popular cuture – and it certainly is in rap music – it's inevitable that some equally vulnerable girls will be drawn towards it.

Common sense dictates that they will be abused as a result, both sexually – being raped by gang members is not uncommon – and by being lured into criminal behaviour themselves.

It is a fact that men commit many more violent offences than women, although violent women – because they offend cultural notions about women being the "nurturing" sex – tend to get heavier sentences; when taboos are broken, people are horrified and excited in about equal measure, something that's worth bearing in mind whenever the subject of female violence returns to the agenda.

This week's horror stories about girl gangs are a perfect example; they are strikingly short on hard evidence but long on hair-raising interviews with kids who claim to have personal experience of the phenomenon. "I can show you six or seven [girl gangs] in one area", claimed an excitable interviewee on yesterday's Today programme.

This would suggest that London has dozens, if not hundreds, of girl gangs rampaging through the streets and causing mayhem. Yet the Metropolitan Police is aware of a total of 170 gangs in the capital and, of those, only three are exclusively female. This hasn't stopped the BBC returning to the subject throughout the summer, with Woman's Hour and a Radio 1 documentary entitled Mean Girls blazing the trail for yesterday's Today investigation. "Shock! Frenzy! Devastation!" Sorry, I'm talking about Attack of the 50 Ft Woman again, although there's clearly no shortage of kids in 2007 who are willing to tell reporters about muggings and robberies they have witnessed or taken part in.

Such claims are impossible to verify, especially when the interviewees are identified only by a first name; some of them sound very much like teenage bragging. What is needed to justify all these colourful claims is some statistics, and they have been noticeably absent. "A BBC investigation for the Today programme has found that an increasing number of girls are operating in gangs, some as young as seven", James Naughtie declared yesterday, yet the report which followed offered no hard evidence for the proposition. Naughtie suggested that girl gangs are "prevalent", which certainly doesn't match my experience.

Two months earlier, there was a surreal discussion on Woman's Hour which simply assumed that girl gangs were a growing problem. Jenni Murray, usually the most sensible of interviewers, asked how this situation had come about and what should be done without ever establishing that the problem really existed.

The item was prompted by a real event, the fatal stabbing of a girl in Croydon a week earlier which was said to have followed an argument between the victim and a girl gang, and the programme claimed there had been "an increase in reported incidents of girls' involvement in gang violence".

Once again, this is an imprecise formulation which could mean one of several things – that more girls are being drawn into boys' gangs, as girfriends for instance, or that there has been an increase in girls forming their own gangs.

Susannah Hancock, London regional manager of the Youth Justice Board, thought the first explanation was more likely, telling Murray that boys' gangs were getting younger and that more girls were becoming involved on the periphery – to carry drugs, for instance. She emphasised the danger of classifying any identifiable group of girls as a gang, a point which shouldn't need making given the propensity of girls down the ages to form close friendship groups without necessarily involving themselves in anything worse than sharing lipstick.

Three months ago, the Youth Justice Board addressed the subject of young people's involvement in gangs and stressed the importance of making a distinction between "real" gangs and groups of young people who may commit low-level anti-social behaviour. "Mislabelling of youth groups as gangs runs the risk of glamourising them and may even encourage young people to become invoved in more serious criminal behaviour," it warned.

This is a real danger, and one of the few sensible observations that's been made about the subject in recent months.

Another danger is that we start seeing "gangs" on every corner, further alienating kids who are suspicious of adults but haven't yet got involved in criminal behaviour. I'm still no wiser about the number of girls involved in gangs, but you'll have to excuse me while I check my windows – I just can't stop thinking about that 50-foot woman.