The number of women in prison has grown at nearly twice the rate of men in the past 23 years.

A Department of Corrections report shows between 1986 and 2009 the number of women being sent to prison grew by nearly 300 percent.

The growth rate for men is around 160 percent.

Corrections spokesman Dr Peter Johnston says the number of youth prisoners has decreased. He says the report also shows there were twice as many Maori males aged 25 in prison compared to European males.

Dr Johnston says prisoners are having longer offending careers.