The extension of a scheme giving young offenders a second chance to avoid prison, revealed by The Herald yesterday, has been decried by Tories as a "soft touch".

The extension of the "structured deferred sentence" scheme to Glasgow and Tayside follows a successful trial in five areas. The approach is aimed at minor offenders with problems such as drug or drink abuse, learning difficulties, or unemployment.

After conviction but before they are sentenced they receive help from social workers and other bodies with the aim of improving their behaviour. When they are sentenced, three or six months later, the extent of their co-operation is taken into account.

The scheme has so far been operated at sheriff courts at Arbroath, Ayr, Forfar, Kilmarnock, and Inverness. Research into the operation of the scheme, published yesterday, said those involved in the justice system and some offenders believed it filled a gap in the options available to courts. The default rate, of around a fifth of those taking part, was said to be lower than in community service or probation and the scheme specifically excludes those facing violent or sexual offences.

But the Tories castigated the announcement. Their justice spokesman, Bill Aitken, said: "The SNP's desire to create a Soft-Touch Scotland knows no bounds. Today they want to extend a scheme which allows criminals to breach the terms of being spared jail but not face any consequences for up to three or six months.

"Prison serves four functions: to punish, to deter, to protect the public, and to rehabilitate. However, as is now abundantly clear, the SNP is driven by a compulsion to empty our prisons regardless of the consequences.

"If a court believes that a criminal deserves a prison sentence, then they should be sent to jail."

But Justice Secretary Kenny MacAskill insisted: "The schemes are now running well and are having positive effects on the root causes of offending behaviour. It is also encouraging that sheriffs have expressed confidence in them. We are not talking about violent, serious and dangerous offenders."

Labour established the original pilot scheme in 2004.

Labour's shadow justice secretary Pauline McNeill said yesterday: "Labour supports the principle of Structured Deferred Sentencing, but we are concerned that it has been rolled out at a time when the SNP are under pressure on prison numbers."