National data has shown there has been a 13 per cent increase in females in custody in the past year nationally and an 18 per cent rise in Aboriginal and Torres Strait Islander females in custody.

Canberra's jail held 12 female prisoners in June 2013 which had risen to 22 in April this year, according to corrections data held by the Australian Bureau of Statistics.

Canberra's male prisoner population has surged dramatically in the past few years, rising from an average daily male prisoner population of 228 in 2011 to 319 incarcerated at the same time this year.

The ACT Government has begun work to construct two new blocks at Canberra's jail to alleviate overcrowding and allow more separation between prisoners.

Australian Bureau of Statistics director of the national centre for crime and justice statistics William Milne said the overall number of people in custody in Australia increased by 11 per cent nationally between the June quarter 2013 and the June quarter 2014.

ACT Corrections Minister Shane Rattenbury said the new cells at the jail would be bigger than the old ones.

The new blocks will increase the jail's capacity to 480, with room for more if prisoners were kept two to a room.

Mr Rattenbury said the high number of inmates put constant pressure on staff trying to separate prisoners of different security classifications and different needs and prisoners who needed to be separated because of previous connections in the community.

This has been a particular problem in Canberra because of the small jurisdiction and only having one prison.