A Victoria University researcher says New Zealand is not alone in sending more women to prison.

A Department of Corrections report shows the rate has grown at nearly twice that of men in the past 23 years. Between 1986 and 2009 the number of women sent to prison grew by nearly 300 percent.

Dr Venezia Kingi says the increase is no surprise and could be down to a number of reasons. Dr Kingi says one is greater equity in the way male and female offenders are being treated. She says in the past, women behaving a certain way may have been treated in a discretional manner, but they are now being arrested and charged.

However, Dr Kingi she says there is still a huge difference between the numbers of men and women behind bars. She says fewer than 400 women have been sent to jail in the last 23 years, compared to more than 6,000 men.