About 70% of female inmates had been unemployed
There are now a record 4,045 women in jail in England and Wales and numbers have almost doubled in the last six years and gone "off the graph" in the last three months.
Prison Service Director General Martin Narey said the cause of the steep rise was two-fold:
But campaigners for penal reform believe they might have some idea.
Charlotte Day, policy officer at the Howard League, told BBC News Online the sudden increase, which "massively outstrips" rises in crime, suggested there had been a change in sentencing practice rather than a change in women's behaviour.
'Inherent sexism'
This could be due to magistrates getting tougher on drug-related crime, for which women are increasingly being convicted and which tend to carry tough sentences. she said.
Ms Day said there could be an inherent sexism in the sentencing process, with women attracting harsher sentences than men - particularly in the youth courts.
"When a woman commits a crime the courts are likely to view her as having transgressed not only legal law, but also the idea of feminine behaviour...so she's seen as even more deviant.
"They would see it as 'If this girl has done that then something must be going badly wrong' - whereas with boys it would be seen as almost normal."
Juliet Lyon, director of the Prison Reform Trust, said judges and magistrates were not making enough use of alternatives to prison.
She told BBC News Online: "The use of jail is out of all proportion to the types of offences being committed.
"They need to have more confidence that there are other effective options around."
'Tragic lives'
She agreed that what Ms Day called "quite tragic life histories" lay behind much female offending.
Ms Day said the Home Office's own figures pointed to a "catalogue of need" among women offenders.
For example, 1998 figures showed 70% had no job before being imprisoned; 10% had been homeless; 40% had been addicted to drugs and 20% had spent time in care.
Women from such backgrounds were likely to lead dysfunctional, chaotic lifestyles with not much hope of improving themselves, she said.
If their problems are not tackled at "root" level these women would simply keep offending - which would lead to magistrates handing down longer and longer prison sentences.
Ms Ower agreed: "What's clear... is that you need to go back to the circumstances from which those women have come, to which they will return."
The campaigners also agreed that prison just makes life harder for women - so they are more likely to reoffend.
Nacro, the charity for the resettlement of offenders, has said: "Most women in prison receive little help and support and face an uphill struggle to find work, housing and rebuild family relationships on release.
"It is little wonder that nearly half of women released from prison commit another crime within two years.
"This is not only costly for the women concerned but for society as well."
Ms Day agreed: "Consideration has to be given to the knock-on effects of even a relatively short-term custodial sentence. Otherwise you're just creating more and more problems for the future."