Former Scottish secretary Alistair Carmichael has called for prison sentences of under 12 months to be replaced with community measures – in all parts of the UK.
The northern isles MP pointed to the situation in Scotland where there is already a presumption against custodial sentences of less than three months.
It means a court has to actively consider whether prison is the most appropriate disposal and explain why.
Mr Carmichael, the Liberal Democrats’ home affairs spokesman, said: “Now the Scottish Government is looking at going further because in fact three months has been a good start but does not go far enough.
“And that makes sense. The evidence is there. Short sentences do not work.”
He told the Liberal Democrat conference in Brighton that almost half of those released from prison will go on to be re-convicted within the year.
This jumps to 60% for those serving sentences for less than 12 months.
He added: “The evidence is clear – custodial sentences of less than 12 months fill our prisons, make rehabilitation more difficult and we should not be afraid to say so.
“Personally, I want to see a presumption against prison sentences of less than 12 months in all parts of the UK.”
He said he was not naive, accepting prison will always be necessary.
But he added: “It should be reserved for those who have committed the most serious offences and pose a real risk to public safety.
“For the rest, tough community sentences where the public can see justice being done are more useful and appropriate.
“Tagging, meaning that curfews and other restrictions can be enforced and monitored, at far less cost to the state.”
A Scottish Government spokesman said it is committed to reducing the use of imprisonment, particularly “ineffective short term imprisonment”, in favour of greater use of robust community sentencing.
He added: “We’re taking forward a range of measures to support this.
“This includes the consultation on proposals to extend the current presumption against short sentences and the responses we received are informing our next steps.
“We have also invested an additional £4million for community sentences in the 2016/17 Scottish Budget.”