Tasmania's Attorney-General Vanessa Goodwin has said she will push ahead with plans to scrap suspended sentences despite new figures showing the state's prison system is already nearing capacity.

Figures from the Justice Department show only 80 out of the 513 beds in the Risdon Prison complex were free, creating concerns the system would not cope if the Government pushed ahead with phasing out suspended sentences.

About 100 suspended sentences are handed down each month according to the Department of Justice.

Despite cuts foreshadowed for Government departments across the board, Ms Goodwin said suspended sentences would be scrapped no matter the price.

She said options like home detention may actually see the prison population drop.

"We're talking about phasing out suspended sentences and phasing in a range of alternatives," Ms Goodwin said.

Available beds at Risdon Prison Maximum security: 16

Maximum security: 16 Medium security: 8

Medium security: 8 Minimum security: 44

Minimum security: 44 Women's Prison: 12

She has ruled out housing inmates in shipping containers as they have in Victoria since scrapping suspended sentence.

Greens MP and former corrections minister Nick McKim said the Government's plan would lead to overcrowding, reduced rehabilitation opportunities, assaults on prisoners and guards and more crime.

"It's throwing a grenade into the prison system," he said.

"The insanity of Dr Goodwin's policy - and she knows this because she's a criminologist - is that prison should be a last resort.

"Because if you want to run a corrections system to reduce crime, and therefore reduce the numbers of victims of crime in our community, prison should be a last resort."