Opposition justice spokeswoman Vanessa Goodwin announced the policy yesterday, as part of the Liberal Party's ``tough on crime'' measures.

Dr Goodwin said the opposition would abolish suspended sentences within its first term of government and replace them with a suite of alternative sentencing options, to be determined by the Sentencing Advisory Council.

``We're basing this on our belief that suspended sentences are an ineffective sentencing option that do not have the confidence of the community,'' she said.

Attorney-General Brian Wightman said it would have cost the state an extra $4.4 million to jail the 156 people who received a suspended sentence in 2011-12.

Greens leader Nick McKim said the proposal was extremist and unfounded, adding: ``As a criminologist, it is very surprising that Vanessa Goodwin would ignore the overwhelming evidence [and favour] such populist chest-beating.''

Dr Goodwin said the policy had not yet been costed but would not necessarily result in more people going to jail.

She said recent police statistics from Victoria showed a reduction in some crimes since that state moved to abolish suspended sentences in 2010.

Law Society of Tasmania president Anthony Mihal said the very nature of suspended sentences meant they could only be replaced by actual imprisonment; anything else would be considered a lesser punishment.

Mr Mihal said Victoria's attempt to phase out suspended sentences had been ``disastrous'', with prisons so crowded the government was required to buy shipping containers to house prisoners.

Productivity Commission figures released this week showed a 12 per cent increase in Victorian prisoner numbers and a 1.7 per cent increase in reoffending over the past two years.

University of Tasmania professor and Tasmanian Law Reform Institute chairwoman Kate Warner said more sentencing options would be welcome but it should be up to the Sentencing Advisory Council to decide whether abolishing suspended sentences was the best way to reduce crime rates.

Professor Warner said her 2008 study, which Dr Goodwin said had informed the policy, should not be used as justification because while it found there was confusion about the ``apparent illogicality'' of suspended sentences, it recommended against restricting the court's ability to impose them.

That report also said suspended sentences could reduce reoffending: a 2004 study of Tasmanian offenders found that the recidivism rate following a wholly suspended sentence was 42 per cent, compared with 62 per cent from actual prison time.

Offenders aged 18 to 24 were almost twice as likely to re-offend following actual imprisonment than following a suspended sentence.

Professor Warner said alternative sentencing options like home detention would require significant investment to be effective.