There are "worrying" signs of growing violence by women, including knife-wielding girl gangs and "appalling" torture of other females, according to Scotland's top law officer.

Elish Angiolini told MSPs yesterday that while most offences carried out by females were "acquisitive" crimes such as theft or fraud, more women are being jailed for aggressive behaviour.

Speaking at a hearing of Holyrood's Equal Opportunities Committee into women prisoners, she suggested that could be connected to increasing levels of binge drinking among young women.

Ian Gunn, governor of Cornton Vale, told the committee that some women regularly in trouble with the law can spend the equivalent of an entire life sentence in jail over a long period of years.

Ms Angiolini said: "Many women are not simply the collaborators, going along with a dominant male partner, being an accessory, carrying knives for boyfriends, assisting in cleaning up after a murder, etcetera - but are prime movers in some of the cases.

"We have seen some appalling acts of torture by women against women, we have seen increasing signs of groups of young girls using knives, against predominantly other young girls, and carrying weapons."

Ms Angiolini said the violence was "aligned with" increased drinking by young women: "And in the drugs world there are a very small number who are leading groups and gangs in drugs."

The committee was told many of the women in Scottish jails are as much victims as criminals, and that the main women's prison at Cornton Vale can be a respite from the chaotic and abused lives that inmates face outside.

While the Lord Advocate said women's violence involved "very small numbers" compared with men, she pointed out: "It's not simply the case that all women are there because of their vulnerability." The number of women in prison has risen by 90% over the past 10 years, compared to a 16% increase in the male prisoner population over the same period.

Mr Gunn told MSPs inmates have complex, multiple problems with mental health, drug and alcohol abuse. They are also victims of abuse.

"Being a victim of abuse is something that male and female offenders suffer from, but there are much higher levels in the females that come into our prisons," he said.

Criminologist Dr Nancy Loucks said there should be smaller jails across the country, meaning female offenders could be closer to their families.

She said: "It would be sensible for them to be housed in smaller, more locally-based establishments, where they would have access to services, as well as family contact."