CRIMINALS who have not committed serious offences are being sent to jail because prisons have become too attractive compared with non-custodial options, an academic has warned.

Leading professor of law and criminal justice Cyrus Tata said prisons had become far less degrading than they used to be, and had got better at addressing the complex issues behind much offending. As a result, they can be seen by sentencers and social workers as the best option for vulnerable criminals, particularly women.

However Professor Tata, of Strathclyde University's Centre for Law Crime and Justice, is calling on politicians to make it clear that prison should only be used where a person's crimes merit it, and not because there is no other help available in the community.

Professor Tata said there was a need for more research on the use of 'benevolent imprisonment' but that there was already strong evidence that it is happening, as an unintended consequence of improved work, training and care behind bars.

Writing in the journal Scottish Justice Matters, he added: "The Scottish Prison Service is transforming itself by focusing more on rehabilitation. This is a welcome development. Yet there is an unintended consequence of that transformation: custody may become a more alluring sentencing option.

"This creates a serious risk that more non-dangerous people will end up going to prison, not because the seriousness of their offending requires it, but because of a benign desire to address their needs."

He stressed that he was not criticising sentencers, but calling for greater clarity about the purpose of prison.

Justice Secretary Michael Matheson recently launched a consultation on extending the definition of such short sentences from three months to six, nine, or 12 months, but with sentencers still able to use short sentences if they think it is 'appropriate'.

In a letter to Holyrood magazine, to be published today, Professor Tata says the phenomenon of 'benign sentencing' could undermine ministers' current attempts to reduce the number of people sent to prison, by cutting down on the use of short sentences.

"To preclude this unintended consequence, we need, as a society, to spell out that, unless warranted by the seriousness of offending, no one should be imprisoned for the purpose of rehabilitation," he said.

Professor Tata also said the financial pressures on charities and public services could also help make community sentences less effective or attractive as budgets for alternatives to custody are cut. Already community-based services are under pressure to prove their effectiveness in a way that prisons are not, he said.

Meanwhile women offenders in particular can be seen as candidates for 'benevolent' imprisonment, he claimed, particularly if they had chaotic lives, drink or drug problems, or even if they were victims of domestic violence 'to give them a break'. This harks back to a Victorian belief in the power of institutions to reform people, he argues.

"It is not uncommon for practitioners to talk about women who have repeatedly committed relatively minor offences or not complied with the terms of their community-based orders, as benefitting from a spell in custody as a place of help, protection and sanctuary, or because nothing else seems to work."

David Cross, a leading criminal justice social worker in Edinburgh, backed the concern over 'benign' sentencing. "I frequently hear the argument that those - women or men - 'who have repeatedly committed relatively minor offences, or not complied with the terms of their community-based orders' might benefit from a spell in custody as a place of help, protection and sanctuary, or, because nothing else seems to work," he said.

The chief executive of the Scottish Prison Service, Colin McConnell called Professor Tata's argument "thoughtful and thought provoking. He added: "There are indeed many challenges that need to be overcome if we are to achieve a better balance in response-led resourcing and sustaining a positive impact across the criminal justice system here in Scotland. I think [Professor Tata's] contribution helps move us forward with that quest."