Increasing numbers of violent women are stretching police resources, a police association has warned.
About 240 women a day are arrested for violent crime in England and Wales, according to recent figures.
Police in Scotland and Northern Ireland say, anecdotally, they have also seen an increase in female violence.
The chair of the Police Federation of England and Wales, Paul McKeever, said there was a "new phenomenon" of women using violence and joining gangs.
Mr McKeever said: "Clearly there is an increase in the number of women who use violence in their everyday life and when they are out drinking on the streets around the country."
Young women were also forming all-female gangs or becoming part of "violent robbery gangs", he said.
"It's a new phenomenon and it does stretch the resources of the police service."
According to recent figures from the Ministry of Justice, 240 women a day were arrested for violent offences in England and Wales in 2006/07.
Traditionally young women have been much more informally socially controlled than young men, and we may be seeing some changes
Professor Susan Batchelor
And figures released in May by the Youth Justice Board said the number of crimes committed by girls aged 10 to 17 in England and Wales had gone up by 25% in three years to 59,000 - with significant increases in minor assaults, robberies, public order offences and criminal damage.
Men and boys are still far more likely to be involved in violent crime, however.
Crime reduction charities agree there is an increase in female violence. But they say that often police deal with violent women formally to meet their targets.
The chief executive of crime charity Nacro, Paul Cavadino, said crimes by girls such as fights in and around school would have been dealt with by more informal methods a few years ago.
But now they are "more often dealt with by more formal methods like reprimands, final warnings and prosecution".
Professor Susan Batchelor, of the Scottish Centre for Crime and Justice Research, said violence carried out by young women was "newsworthy" specifically because it was quite unusual.
"Young women are seen as the future of the population and we have much more concerns about their behaviour," she said.
"Traditionally young women have been much more informally socially controlled than young men, and we may be seeing some changes."
This is denied by police forces, who say they target violent behaviour whoever is committing it.
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