It follows an announcement the SNP will bring forward a presumption against sentences of less than 12 months.
The Scottish Conservatives said 11,195 offenders were sentenced to 12 months or less in 2015/16, including those convicted of homicide and sexual assault.
Scottish Conservative shadow justice secretary Liam Kerr said: “The SNP is creating an impression that this change will only really impact low-level offenders whose rehabilitation would be better served with alternative punishments.
“But the reality is it will see certain offenders convicted of homicide, serious assault, attempted murder and sexual assault escape a jail term. That’s a shocking way to treat victims of crime, and will do nothing to help rehabilitation.
“Prison is meant to do four things; punish, deter, keep the public safe, and rehabilitate.
“With these proposed changes, the Scottish Government is utterly neglecting all but one of these.”
A Scottish Government spokesman said: “These claims are wrong. We have set out a presumption not a ban as sentencers retain the discretion to pass the most appropriate sentence based on the specific circumstances of each case.
“We are clear that prison remains the right place for the most serious and dangerous offenders.
“Evidence shows that short-term imprisonment is not effective and can often increase long-term offending; individuals released from a custodial sentence of 12 months or less are reconvicted nearly twice as often as those who are given a Community Payback Order.”