Women in parts of the north of England are four times more likely to end up in jail than female offenders in the South, research suggests.
A report by the Prison Reform Trust found that Cumbria has the third highest rate in England and Wales with 50 women per 100,000 in the police force area being handed an immediate custodial sentence.
By contrast, Sussex with 15 and Surrey with 16 per 100,000 have the lowest rates.
The analysis is published on the day the Trust convenes a Women's Summit, bringing together ministers, senior police representatives, Government officials, women's services and women with experience of the criminal justice system.
Jenny Earle, who leads the programme to reduce women's imprisonment, said: "The Government has promised to reduce the imprisonment of women and the inter-generational harms this causes.
"Impressive work in some local areas to reduce the number of women entering the criminal justice system is bearing fruit.
"But we have yet to see the decisive action - including a prohibition on short prison sentences and investment in women's support services nationwide - that will put an end to the postcode lottery in women's justice."
Latest figures from the Ministry of Justice show there are just under 4,000 women in prisons in England and Wales, compared with nearly 80,000 men.
Females represent around 5% of the total prison population, a proportion that has been consistent over the last decade.
- The figures relate only to women who have been handed an immediate jail term - not those who receive a suspended sentence.